Not the best rule at all. Could use an update. Events in Upkeep should all happen at the same time. Much easier for players.
I cannot agree about "Events in Upkeep should all happen at the same time" as that would eliminate the Initiative marker's mechanic which the game is built upon.
I would rule that if there is a creature with a Burn maker in the same zone as he at the beginning of the Upkeep phase that Skeelax would gain the Regenerate trait. He would then keep that trait until the next Upkeep phase.
No offense sIKE, but that would needlessly complicate matters imo.
Every part of the game of Mage Wars revolves entirely around the INITIATIVE marker.
Initiative decides who goes first and who goes second in every phase of the game.
The same applies to the upkeep phase.
So, I don't see what's "wrong" about Skeelax
The person with Initiative resolves his upkeep effects first ( in the order he wishes them to be executed ) followed by the other player.
If the Skeelax player has initiative he can activate the regenerate ability before there's a Burn roll. If he doesn't have initiative, it's
possible that his Regenerate ability does not trigger if the burn counter has disappeared before he gets a chance to trigger his Regen ability. Simple as that.