How about a Conquer the Flag Game Mode. Simple concept but probably a lot of fun playing teams. The objective to go into enemy territory and grab the flag and be able to hold it for 1-2 turns (could be a game setting option). The player that holds the flag has to survive the specified turns in the same place where the flag was. When units are killed they are re-spawned in the middle of the map or at the edge of the map if the flags are in the middle. If nobody conquered the flag in an optional time-frame (5-10-15-20-30 minutes) then the team with the most kills wins.
A "respawing hero" also opens up possibilities for numerous other game types. For instance, we could have a Mage/Guardian frag fest game type where each player controls only one hero at a time and the goal is for your team to kill a certain number of enemy heroes. When your character dies, you can pick a new class and respawn in your team's base.
Great thinking on Capture the Flag (fyi, this was my favorite game type in the original Star Craft).
The
QuoteMage/Guardian frag fest
sounds like fun idea also. I played a lot of Capture the Flag in WOW and it was a lot of fun. I don't think Hero Mages is suited to be done the same way, that is to have to bring the flag back to you team base, but I remember having played another game were you just had to hold the flag for some time on the opposite teams place and that was fun too. That's why I called it Conquer the Flag :) but the name is not important.
perhaps one flag in the middle and you have to take it to the enemies side.