anything /Rad and anything /Kin are popular for grouping. /Storm is just extremely good for damage and debuffing. If you get really good with hurricane you can carve any group into a tight little brute sandwich with fireball filling and the -tohit means that they won't bother you too much with return fire.
I have an AR/Rad an AR/Dark. Both are excellent on teams and mow down groups with amzing efficiency.
Ice/Kin is good solo, and as kin you'll automatically be good in groups.
Elec kin is okay solo and again /Kin is always good in groups. This setup has the added benefit of the sapping element. If you slot the three attacks that have a chance to grant you end with two endmod's and two end redux they become nearly zero cost. The problem I had on my Ice/Kin was that in groups I would run out of end too quickly pre-transference. I did not have that issue with Elec/Kin.
I also found Dark/Cold to be a terrifyingly effective combo. Dark gives you some battlefield control and supplements your debuffs. Cold gives you pretty much the second most complete set of debuffs in any set. The buffs in cold are always welcome as well. It is possible to go with setup without taking any of the buffs if all you want is solo, but at least take ice shield if you find youself on a team sometimes. Those little icicles increase people's perception of you and makes it more likely that you'll be asked to group with them again.