I'm in a bit of a quandary regarding the enhance two piece. Our current raid team has quite a lot of competition for the shammy/monk/warrior/hunter tokens so while I'm gearing up nicely with non-set pieces, I was unsure if I should be trying to get my 2 piece even if it meant replacing same level gear pieces at the expense of other raid members who haven't upgraded that piece from last tier.
I've heard mention that it can be as much as 6-7% but have seen no confirmation of it's exact strength, however if it *is* that strong I would feel more than justified rolling for the token.
I can't say how strong it is entirely, as I am no a math whiz. But the difference in my numbers was significant when i picked up the 2 piece. Now given I also upgraded from a 530 to a 561 when I got the piece so that contributed. In my logs it accounts for roughly 3.4% - 4.5% of my damage, and with the increased UF uptime it could easily clear that 6-7% mark.
Even more so on Aoe fights, as you get more empowered fire novas. I absolutely recommend rolling on tokens.