Yes, it would be fair decision if he'll be able to regen only while fighting, and as I mentioned it was some kind of mini-boss during 1st phase of fight in previous versions - something like Lich from wc3 - he was summoned alone.
And increasing the fighting time of Yurgimar himself will be nice - now it is about 5 second while he is on the ground and then he flies away.
Maybe reduce the number of red-blue-yellow circles events during 2nd phase of fight? I mean if now it occurs for example once per 1 minute maybe increase it 2x times - once per 2 minutes?