Questions about mulyiplayer and achievements.

[Super Bad]

Answer these it will be a big help.
>Is there an achievements that are related to story difficulty?
I checked but can't find any, just want to make sure by asking
>Is multiplayer still populated?

[(+[Coffee]+)]

1st question:
No, there aren't any achievements that require you to play on Easy, Normal or Hard difficulty.

2nd question:
Yes mutiplayer is still rockin' but you'd be best to switch off any DLC maps you may have.
This makes for finding matches quickly, plus the DLC maps aren't required for achievements anyway.
Use this guide for reference:
http://steamcommunity.com/sharedfiles/filedetails/?id=285216539

Our Steam Group, Tomb Raider Multiplayer Madness (TR-MM) may be able to help you out, so check the event times:
http://steamcommunity.com/groups/TombRaiderMPMadness#events

Sundays are achievement based matches and we start in about 15 minutes if you're around?
See you there maybe

[Super Bad]

Thanks a lot for the reply and awesome group, I will definitly join your group events! =)