Back in the day, I played a fire mage. I now play shadow. My understanding with Fire is once you hit TBC and Wrath there are certain points with a high crit rate where it makes sense to Fireblast on every cooldown to keep that ignite stack growing is my understanding. You're mostly spamming fireballs and stacking scorch. Ideally, you have a scorch specific mage, but I find stacks are less likely to fall off if mages are working to maximize their dps as a group and not individual dps.

Is there a crit point say 70% to 80% where it makes sense to fireblast on cooldown just to grow ignite more from that instant crit? Definitely, if having to move for any reason.

Now, if you keep that ignite as large as possible it's my understanding from playing fire in vanilla overall mage dps increases, while individual mage dps decreases. But, one mage might get full credit for starting the ignite stack. If this is the effect of fireblasting on cooldown isn't it best for overall mage dps with TBC and Wrath changes? You definitely do not use it in vanilla as you cannot get enough crit.