Doing a second insanity playthrough as an Adept, choosing the shotgun specialization. I also did the Collector ship mission using mostly the default SMG, it was pretty fun

, probably because I had Grunt and Thane to back me up. Grunt had Incendiary Ammo and concussive blast, Thane has shredders, a sniper and warp and I had AP ammo, so the collectors actually went down pretty easily. Sniper characters are VERY handy. Use them.
In all seriousness though, Adepts and Vanguards get the short end of the stick at the start of the game, and, hell, their powers are pretty terrible on Insanity due to 100% of enemies having damage protection. The Shuriken is bad until you learn how to rapid fire. Press the trigger at the end of each burst instead of just holding it, and you can effectively fire full auto and get about twice as much DPS. The Tempest is still a little better in terms of accuracy and sustainibility though, so get it ASAP. As for vanguards, the Katana is meh, and the DLC Eviscerator is only slightly better. I like the Scimitar, and I've never tried the Claymore. For powers, I just use Pull followed by some other power, it's really only "for the lulz" as they say.
Will probably try it as a soldier next, if only because I want to try the Revenant.