There are a few places, or bosses, that I have noticed people do not like to bring a tank. Namely the final bosses in Fungal Grotto and Darkshade Caverns. These fights are not necessarily dps checks, but you can't really tank or melee dps these fights. Because of this groups will normally bring 3 dps which will make the healer hate life and groups that are a little less coordinated fail.
What you can do, at least as a Nightblade tank, is to tank passively. For fights where you need to stay ranged there are a few things you can do.
1. Before the fight make sure you have a bow or staff handy. This sounds kind of dumb to say but preparation is important. Do you go out on a date wreaking of body odor and with an empty wallet? Not if you want a second date. Be prepared.
2. Use Shadow Image to keep minor maim on the boss. This will reduce their damage by 15%. Shadow image is a better choice because it is ranged and will keep up with the engine guardian much better than the dark shades morph. Most other bosses are fairly static.
3. You're going to need bone shield. The synergy will give your allies a shield equal to 60% of their max health. It's best to tell your healer to activate the synergy so your healer will only have to heal you.
4. Either morph of consuming darkness will do. However, bolstering darkness will be more favorable for these fights and when reviving allies.
5. Reapers mark. Not a whole lot of useful for tanking, but keeping the mark on the boss will let your dps burn down stuff faster, and everyone loves that.
Other than that do what you can to help out. Tanking the rest of the dungeon is business as usual. But if you're going to tank something you can't conventionally tank, then try it this way.
If anyone has a method to passively tank with a class other than Nightblade feel free to post. Good luck out there tanks, because the IC patch just made your job harder.