There are a few really good maps that do not have timers.
Cults, Xtomic, Krexx, Briggs, Jetta Magenta just to name a few.. ( I personally like Cult's & Krexx ) Jetta's good for under geared farmers and those who don't want to fight EBs.)
It's easy to make custom missions once you understand the system.
But figuring out which powers to assign to the mobs is a little tricky because it affects the XP/inf.
there's not really a good current guide on it any more...
Briggs had one but its outdated..