Back in the day, Fire/kin and Ill/rad were the kings depending on what you wanted. My Ill/rad was the first support character which soloed on +4 while not being level 50(40 for that matter), and used nothing more than common IOs. Now, have any new sets made something which is better, that's up for debate. I think you can find a number of builds which will solo very well. I see no real issues coming from the Dark/dark I made.