I actually judged how effective they were in combat based on the speed and number of people they could take down: 

Orion with Telekinesis can really do some damage, especially if he gets his hands on explosives.
Darrien can potentially turn an orange into a bio-weapon, and if he gets his hands on actual laboratory-grade acids . . .
Heather with electricity does not need to be explained, but it should be mentioned that electricity + iron sand = black waves of death.
Ray could cause instant cancer or just knock everyone out in one go. The wouldn't even be able to dodge.

^Oh yeah, now that you point it out . . .