For me and plenty others several achievements/trophies are bugged. They simply wont pop.
The ones confirmed to be buggy are:
The Banes (Bane of Kell, Bane of the Machine, Bane of the Undead, Bane of the Emperor)
Change of Heart
Lucky 7's
Use of Weapons
Triple Play
Decyptologist
Rising Vanguard
A New Steed
There are three ways which sometimes fixes this bug.
1 - sign out of your account and back in again.
2 - Choose a different Guardian (There are reports of the achievements/trophies popping while the other character loads).
3 - Once in-game, go to your game-menu > Settings > Log Out > Change Profile. Select your account again and the game will reload. Everything should pop then.
These ways are not 100% guaranteed and might not work for you. It worked for me luckily so I can testify that it can work.
Hopefully this bug will be fixed soon. Until then I'll update the glitched achievements/trophies if needed
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Triple Play is bugged on 360, none of these worked for me :/