Mouseferatu
Hero
My previous 3.5e game had no Cleric, Druid or Bard (or healer of any other type). They muddled through okay.
I'd honestly like to see an all-Striker party, to get an idea of what the other roles bring to the table. I'd like to see an all-Leader party for much the same reason.
IMHO it'd be an educational experience for everyone involved. So yeah, if it happens, I'd run with it. When PCs die, players may decide to change role -- but that's up to them. Having a balanced party isn't a guarantee of survival.
Cheers, -- N
I encourage but do not require balanced parties. I'll tell them that they're responsible for making up for any deficiencies they find in their party composition. I'll usually adjust some challenges for the party's composition so that all classes get a chance to hold the center stage, but will also make sure much of it has its own internal plausibility regardless of the current character composition. If that makes things either particularly easy or hard because of character development choices, then them's the breaks. If they consistently have trouble with those segments, I may suggest but ultimately leave it up to them to decide how they want to deal with it.
These.
I do not ever advocate forcing a player to play a particular class or role. Encourage, yes, but never force.
This sort of thing is what I've long referred to as a "self-correcting problem." If the party is going to suffer more casualties because it lacks, say, a leader or a defender, then so be it. Sooner or later, one of the people who dies will come back in the missing roll, and the problem will cease to exist.
In the meantime, let people play what they want, and if it works out, so much the better.