with more crit kindling will definately sync combustion and FO a lot more but you wont use FO every time its off cd, only to maintain your crit streak and with FB having a short cd in itself and you have phoenix flame as well, so you have several tools to extend your crit streak without having to even use FO atleast thats my take on it.
well the softcap for crit is something like 77% crit due to critical mass as that will give your fireball and pyro a 100% to cri and im already sitting at 50% crit in ilvl 835 gear on my mage on beta, could prolly reach 52-54% in fully optimized gear, reaching 77% doesnt seem too far off.