Personally, I found that fire cages didnt need anything beyond the initial 2 Accuracy. It recharges very fast, and the duration is long enough.
I would 6 slot radiant aura, 3 heal 2 recharge 1 end reducers. Its just enough to keep you alive when tanking big groups.
AM Could really use 3 end recovery in it too, but thats not essential.
I would change flashfire to 2 acc 2 disorient 2 recharge as well. Normally back up for every group when you team then.
I wouldnt take ring of fire. At all.
The imps I would change to 2 acc, 3 damage 1 recharge, Or maybe 2 recharge and 1 acc. You tend to lose the odd imp all the time so the recharge is handy.
EM Pulse should be changed to 2 acc 2 recharge 2 hold duration too. Deserves the slots as its so uber 
Might wanna fit in the single target fire attack from the epic too.
Slot RoF for damage, or drop it and put Acrobatics earlier, then take fire blast at 49 and slot it for dmg. 
Hotfeet could use another dam and end reduc.
Consume has worthless damage, it's better to slot it for recharge so it's up more often, IMO.
I have sort of fallen into this build up to 28 so I thought I would try and set out what to do on the way to 50.
1. Char Acc(1), HoldDur(3), HoldDur(5), Acc(7), Rchg(17), HoldDur(27)
1. Radiant Aura Heal(1), Heal(37)
2. Fire Cages Acc(2), ImmobDur(3), Acc(21), ImmobDur(21), Rchg(29)
4. Radiation Infection AccDebuff(4), AccDebuff(5), AccDebuff(11), DefDebuff(11), DefDebuff(34)
6. Accelerate Metabolism Rchg(6), Rchg(7), Rchg(23)
8. Hotfeet Acc(8), Dmg(9), Dmg(9), EndRed(15)
10. Combat Jumping Def(10)
12. Flashfire Acc(12), Acc(13), DisorientDur(13), DisorientDur(15), Rchg(17), DiorientDur(34)
14. Superjump Jump(14), Jump(40)
16. Swift Run(16), Run(49)
18. Cinders Acc(18), Acc(19), HoldDur(19), HoldDur(25), Rchg(34)
20. Health Heal(20)
22. Stamina EndMod(22), EndMod(23), EndMod(29)
24. Enervating Field EndRed(24), EndRed(25), EndRed(36)
26. Lingering Radiation Acc(26), Slow(27), Rchg(40), Rchg(40), Acc(43), Rchg(45)
28. Smoke Rchg(28)
30. Ring of Fire Acc(30), ImmobDur(31),ImmobDur(31), Acc(37), ImmobDur(37)
32. Imps Acc(32), Dmg(33), Dmg(33), Dmg(33)
35. Hasten Rchg(35), Rchg(36), Rchg(36)
38. EMP Pulse Acc(38), Acc(39), Rchg(39), Rchg(39), Rchg(40)
41. Fire Ball Acc(41), Acc(42), Dmg(42), Dmg(42), Dmg(43), Rchg(43)
44. Fire Shield Def(44), Def(45), Def(45), EndRed(46), EndRed(46), EndRed(46)
47. Consume Acc(47), Acc(48), EndMod(48), EndMod(48), Dmg(49) Dmg(49)
50. Acrobatics Rchg(50)
What I found was I had a lot of slots later on that I was struggling to find a place for. Any comments welcome.