Is a Useful Pacifist Possible?

They're not worthless or useless, but I'd choose someone with attacks over a pure healer or pure tanker when making a team.

i am kinda long winded, so bear with me

While those who go pure healer or tanker (wtf is that anyway?) as long as your a good role player and know your role, then i would honestly rather have that. Now, missing that extra damage can possibly be detrimental if your team build isn't tight. It's kinda like when the chicago bulls had jordan, pippen, and rodman. everyone knew jordan and pippen scored the points while rodman got the rebounds. rodman didnt car about or want to score points, and because he was one of the leagues best ever at what he did (while being 6'8"), everyone else could focus on thier game...and it worked well for them. Conversely the Lakers of thier era were more of the type where anyone could have thier night.

With everyone being more multi facited, you can still accomplish the same and sometimes even more, but i am always a sucker for having a guy who either does one thing and does it well, or has a tool box full of all kinda of useful tricks and powers. (like dark defenders, trick arrow, illusion controllers, or people that have stealth/tp, and the rare occation that someone has tp foe, team tp, or a cage/repel and knows how and when to use it!)

bottom line is that if you have 8 people who are good and know thier toon inside and out, you should do well reguardless. (that is given that they slot thier guys decently...)
find you a could of people seem awesome to you and pick their brain, and try to team with them often. I hope you have yourself a very good playing experiance. be sure to pass on your knowledge to anyone who needs it as well!

I don't think any of these ideas are really pacifists. If anything they would technically be enablers.

being able to skip attack powers make the biggest arrgo magnet tank you can and slowly run away from your team like your trying to lead the mobs away.