I think it was about 4 or 5 months before I entered and cleared a savage on BLM. This was while playing the MSQ and other content so would be less actual time I guess. I also think I could have done it sooner than when I started doing high end content.
^ This
BLM for example uses 2 low damage ice spells when entering astral fire, and dots somewhere in there too. So for example: Bliz III > Bliz IV > Fire III > then the main Fire IV / Paradox rotation. I tend to save my first Thunder until buffs are up then refresh during phase changes (whether thats optimal I dont know, Im a casual high end player).
If the raid buffs were applied immediately then its wasted on the first 3 GCD's.