Fire and Brimstone

Speaking purely from a PvP destruction perspective I think we all agree that the current '' Fire and Brimstone'' is a really crappy talent especially for the 5 talent points you need to spend to max it out.

Now I suddenly had the idea along the lines off: Each time your Imolate deals damage ( ticks) your chance to get a critical strike with Incinerate and Conflagerate by 2/4/6/8/10%. Also reduces the chance your Immolate spell will be despelled by 20/40/60/80/100%.

Any toughts on this, would it be too overpowerd or too weak ?