Guild Wars 2

I love this fight as its a real challenge I hope to beat tonight. So my question is this does the heal/stealth go by a timer? If so how long?

If its not by timer then how?

I don’t think my group has the burst potential for the 4/5 method but know a better likely hood of when sparks will spawn would help us. As in they spawn every minute or 30 seconds.

I believe it’s a timer yes. As soon as she gets to 50% HP, Simin will enter phase 2, where she hides every minute regardless of how fast you put the sparks. So the quicker you put the sparks, the longer Simin will remain visible.
Note however if the minute passes and Simin’s health is over 50%, then she will be back to phase 1. Which means that you’ll need to brign her down to 50% HP again to get her in phase 2.