D&D 5E (2014) Seeking information and inspiration

[Tony Vargas]

And in my experience, 5e is way more forgiving in terms of 'balanced party' than 3e or 4e were

5e leaves a lot of the heavy lifting of encounter balance to the DM, so a DM who can handle building encounter for a nominally 'balanced' party can handle building encounters for a graduating class at Hogwarts or a family of Barbarians just as easily. ;P

you can literally all be some kind of sword-swinger and be fine, it's not completely mandatory to save a spell caster, a healer, a skill monkey and a tank, in order to function well day to day.

It's not mandatory, but the other players just might appreciate having a healer if they don't already have one, or a tank to stand at the front if they're going to be fighting in dungeon corridors a lot if they don't already have one. By the same token, if you expect to be fighting in a lot of 10x10 corridors, a third melee guy is not at all welcome...

Even if it turns out they've got their traditional meat-shield, trap-victim, and heal-bot positions already filled, so you can play whatever you feel like, it didn't hurt to ask.