Now you can play with any difficulty with customized value of bonuses for enemies (whatever if enemies feel too weak or too strong for you - with this mod you can tweak it as you like ). 
You want more interesting and tougher gameplay? You can enable enemies shield regeneration like in ME1/ME3 - this is more lore friendly and enrich gameplay by adding sense of more faster action (if you not kill enemies fast enough then their shield start regen ). Optionally you can also enable regenerating of enemies Barriers and/or Armors (regeneration of Barriers is recommended only for advanced gamers and Armor regen is recommended only if you want real hardcore ).

Enemy Shield Regeneration (and Barrier/Armor regen):
-Enemy Shields Regeneration (in short it can be called ESR )- enemies regenerate shield the same like Shepard - so it is about after about 8 seconds shield will start repairing after enemy stopped receiving damage (when enemy will be in cover then Shield regen start after 5 seconds - but you can choose version "Easier" what have disabled faster regen in cover ). 
-Enemy Barriers Regeneration (EBR )- if you want game even harder (I don't recommend this for causal players unless you nerf game with some other mod or lower difficulty ). Some players may find Spectre boss fight with (I don't want spoil for new players and if you played game before you probably know who I mean ) too hard especially on Infinity or when you don't have good build (you can disable mod any time and enable it again later, this is true also for Shield and Armor regen mods ).
-Enemy Armors Regeneration (EAR )- if you want game even more harder. Boss fight in Kasumi loyal mission and Final boss may be too hard. Keep in mind that Krogans and Vorcha already have regen health and Blood Pack Troopers have ability for instant repair armor - so enabling Armor Regen it will considerably buff such enemies. 
-Enemy Geth Shields Regeneration disabled (EGR ) - this disable Shield regen for Geth (using this mod have only sense if you installed ESR and you want disable Shields regen for Geths from some reason ).

If you are using EAR and playing with Veteran difficulty level or below then it is recommended to install Difficulty Level Tweaks (any version but not "0" ) because without that armor of Blood Pack Trooper start instantly regen. Similar bug is with shield of Geth Trooper when using ESR but this is not bothersome as this is easier opponent (but if you want, you can fix this the same way or by installing EGR but it will disable shields regen for all Geth ).

Reasons why this is interesting:
-to make game somewhat harder (or even more harder with Barrier regen or/and Armor regen )
-If you want be more "fair" to enemies (Shepard have shield regeneration on at default )
-If you want game similar to ME1/ME3 and more lore friendly (it is kind of weird that shield regeneration at default not works on enemies only in ME2 )


Difficulty Level Tweaks (DLT ):
At default only Hardcore and Insanity difficulty levels have added bonus to defense for enemies. Hardcore have +75 and Insanity have +150. In short, higher defense bonus = more damage enemies can survive.
With this mod you can customize your difficulty level better. This mod allow you to choose defense bonus (for enemies ) for any difficulty level,
Options are:
+0 (lower enemies will not be protected by shields/armors so you can easily use on them powers. Don't recommended when you using EAR (Blood Pack Troopers will be bugged with instant start of armor regen ). When you using ESR, Geth Troopers will have instant start of shield regen - this shouldn't be problem for most people but in case you can use version below (+1,171875 ) what have very small value added to prevent that or you can install EGR (it disable shield regen for all Geth ).
+1,171875 (this is extremely low value and shouldn't be much noticeable comparing to 0 - some enemies gain armor or shield but really low amount.  )
+9,375
+18,75
+37,5
+75 (such value is in default game on Hardcore difficulty level )
+112,5
+150 (such value is in default game on Insanity difficulty level )
+225 (if you like "sponge" enemies )

Examples of use:
-Some people feel that enemies die to fast on lower levels but on hardcore and insanity have too fast reactions and do too much damage to Shepard and squad. Then adding +75 (or more if you want ) bonus for lower levels makes game more challenging but not too hard.
-Some people feel that AI of enemies at hardcore or insanity suit them best (faster reacting, making more damage etc. ) but with +75 or +150 bonus to defense they pretty tough to kill (some people may call it even "sponge" enemies ).
-to customize to your preferences how much protections you really want for enemies

More information:
Regen mods elevate difficulty level but there is much mods what already lower difficulty. 

Mods what I recommend if you want make game easier:
Modern Weapon Pack - great mod, it add new weapons (you can also check Easy Armor Stats for stats of new weapons and default ones )
ME2 Almost Unlimited Guns (switchable any 5 weapons )
ME2 New Upgrades (unlocked hidden content ) - Cyclonic Array upgrade gives +25% shields for squad and Bovine Fortitude upgrade allow Shepard to survive some amount of damage when health depleted
ME2 Tech and Biotic Powers Penetrate Shields
Remove shared cooldown (or Remove Shared Cooldowns compatiblity patch for No MiniGames and ME2Controller )
ME2 Enemies shooting accuracy

Mod development:
The idea of Shields+Barriers(+disabled Amors ) Regen is known from 2010. I realized how is possible to enable Regen for Shields/Barriers/Armors independently and it allowed me making separate mods for regen of Shield/Armors/Barriers. 


INSTALLATION (ME3Tweaks Mod Manager needed )
1. Download mod
2. Open ME3Tweaks Mod Manager
3. Drag downloaded file into Mod Manager 
4. Select version what you want and click install or import mods (you can unselect those one you don't intend use ). If you import - click mod name on the list and then click Apply Mod at the bottom right of the window.
5. Repeat steps 3 and 4 if you installing more than one mod. 

This is version for Mass Effect 2 Original Trilogy. If you want version for Mass Effect 2 Legendary Edition - it is HERE

UNINSTALL:
In ME3Tweaks click Manage Target (first make sure that location for Mass Effect 2 Original Trilogy is selected ) and find particular mod (it is in default opened bookmark: "Installed DLC Mods" ) - click delete mod.


ACKNOWLEDGEMENTS / CREDITS
Flash - idea of mod

Big kudos for Mgamerz and ME3Tweaks Group for tools what make making and installing mods convenient:

ME3Tweaks : ME3Tweaks Mod Manager


OTHER MY MODS:
For Mass Effect 2 (Original Trilogy ):
ME2 New Upgrades (unlocked hidden content )
ME2 Almost Unlimited Guns (switchable any 5 weapons )���
ME2 Infinite Sprint (run without need of rest after few seconds )
ME2 Skipping dialogues without selecting response
ME2 Auto cover off
ME2 Corpses stay
ME2 Changes for Import Credits from ME1 save (many options )
ME2 Changes for Resources import bonus (many options )
ME2 Crouching plus Better Accuracy (toggle or hold. many key options to choose )
ME2 Toggle Walk (no need hold button to walking )
ME2 No auto weapon swap when gun empty
ME2 Decals stay
ME2 Tech and Biotic Powers Penetrate Shields
ME2 10x Time Speed Up Button ( useful for skipping )
ME2 QoL. mouse acceleration off. infinite run. separate use sprint cover. time speed button. toggle walk

All my mods for Legendary Edition are HERE
Mods for Mass Effect Original Trilogy are here: ME1, ME3