The new MCH likely carries old unfixed issues

[Sigiria]

Sure but with 6 Heat blasts in that window you'll get 3 charges of each back so you'll end up having to weave anyway cause remember heat blasts reduces the recast of both GR and Rico by 15 sec

you can only put 5 heat blasts on the 8 seconds of the overheat (6x1.5=9s) So if you've emptied your charges you'll still have 15 seconds to use one charge of each oGCD

Edit: Scrap that, since you actually do shot>1.5>shot>3.0>shot>4.5>shot>6.0>shot>7.5>shot. You should indeed have the time to use 6 heat blast, still I feel like it would be better to not risk losing one GCD on the wildfire for the few seconds you'll loose on overcharging the oGCD.