Back in the day (pre-Homecoming, waaay before the Tanker buffs) I had a Fire/Fire/Pyre Tanker with IO sets. She was able to chain Fire Sword Circle, Combustion, Fireball, Burn continuously, with only a fraction of a second hesitation in the chain. Fire Breath didn't fit the concept, but no doubt is decent now.
I have rebuilt her on Homecoming although she's not fully IOed yet at 43, nor does she have Fireball yet. But the 16-target caps, greater damage base, and improved radii are huge improvements!
Both versions used 5- or 6-slotted Fire Sword, Incinerate and Greater Fire Sword for single-target, and I'm personally happy with that chain, although I'm not an attack chain guru. Fire Sword makes up for being the lowest damage of the three with blazing animation speed and good recharge, great for tapping when you want to get damage in right now.