Great guide, really. You echo a lot of my experience on my spines/fire thus far. I PL'd my own spines/fire to 50 a couple of weeks ago. I am starting to IO him up, but as you know, it is expensive. A couple of thoughts:
1) I tried using Burn and TT. It is pretty much useless for farming (or anything, really), and I'm glad to see you agree. Also, not going the burn...TT route gives you an extra 4 power picks.
2) I was hoping that my spines/fire would be a faster farmer than my fire/kin. She's got 4 purple IO sets and a few other recharge bonuses, so her recharge is usually in the 160-180% range (w/ 2-3 siphon speeds stacked). My spines/fire has 2 purple IO sets so far. Anyway, the fire/kin blows through mobs much faster (and, frankly, more safely) than the spines/fire. I watched your demo, and I was impressed. Your spines/fire definitely runs through mobs much faster than my spines/fire. BUT, my fire/kin blows through equal sized groups of +2's much faster than your spines/fire does +1's, and with less $$ invested in IO's.
I don't think you were claiming that spines/fire is a better farmer than fire/kin. I just wanted to clarify for those peeps who were thinking about levelling a spines/fire to make a better farmer than a fire/kin. If you put the same amount of money in the builds, the fire/kin will win every time, IMO.
Now, having said that, the spines/fire is a lot of fun, and more fun to take on TFs and other teams (especially when exemplared).