If beta is any indication, Protective Fighters are the least played "Archetype", so you should not have any troubles finding a group whether you are a warrior, paladin or dread knight.
As for comparision towards Dread Knight and Paladin and what makes a Warrior stand out...the question was asked multiple times on the beta forums but never got a reply.
From what I understood from reading the beta forums, the things that differ a warrior from the others are/were supposed to be:
1: Higher DPS (Dual Wielding probably, doubt it'll happen in defensive stance)
2: Highest defense/mitigation bonus? (A bit unsure of this, but I think I saw numbers around War: 15%, Pal: 15%, DK:10% plus 1% per DC)
Corrected after edit, we're same as pallies, though Venge stated in another thread that "the warrior can reach the highest mitigation levels of all protective fighters. We have the most abilities to do so"
3: Best aggro generation toolset (AE taunts etc)
4: Commands/Battle shouts
Some argue that #4 will just create alot of button mashing.
Maybe it will, but I'll tell you that I appreciate a command where I can target that pesky ranger/rogue/sorc/whatever that's grabbing aggro off me and back him off / decrease his aggro....button mashing or not
We are more weapon dependant than the other two classes though since we have no spells to increase our damage output with, but if you dual wield 2 nice weapons, I doubt a DK will outdps you pre DC4ish, if even then. Never grouped with one high level though for reasons stated below, so I might be completely wrong and we get outdps'ed, meh. Time will tell.
If things turn out to be unbalanced/unfavorable for warriors I believe it will be corrected eventually. Might take awhile, but gotta have some faith
I never got a warrior up very high, partly because I wanted to save some adventuring until the game was properly released, but maybe some of the older more experienced warriors can fill us in on the higher level game and correct me if I'm wrong somewhere
Lotta rambling there, but the base thing is that I dont think you'll have any problems finding a group as a tank
(Edit: Fixed a number that was off)