My understanding (not necessarily correct!) ...
If we are on the same team and a baddie who is +5 or lower is defeated - no matter who does the final blow, or even no matter who does any damage - then all teammates get to share the XP.
The XP awarded is based on your fighting level, with higher XP given for someone a larger # of levels higher than you... so if you are not SK'ed you get more XP (no shock there).
But of course be warned that if you are unSK'ed at level 14 and I defeat a level 20 then I think you'd get nada, whereas a level 19 defeat would be mucho XP for ya so would be totally worth being part of the team. That's from what I understand. I may be off by 1 or something here.
And yes, the XP may be split amongst the team (proportionate to each hero's level), but the *total* XP given is a bit greater (scaling dependent on # of team members) so with a duo it's not too bad, since while one hero is pausing to recover some endurance the other might still be ringing up some XP sales in the ol' crimefighting cash register. When I was starting Captain Puncho, me and a blaster of the same level were teamed and street-fighting in two different areas in the same zone, and thus got faster XP than if either of us were on our own. I'm not sure how much more, but it was noticeable. B)
Anyway, I certainly enjoyed the change of pace doing a door mish, especially as part of a story arc... but next time I'll pick a Lost/Skulls/Hellions or even Council villain since they are more close-range-pain baddies.

That is, if you're interested. :huh: