Did Lamasu die and get revived?

Yes, that is how it typically works.  Lamasu gets killed immediately and is revived by Sulfuriyon on his first turn, but Chimera has almost always attacked Lamasu on subsequent turns until this week.

On NM, Lamasu is probably killed on the opening move about 70% of the time.  On UNM, that is more like 90% of the time.

Doesn't everyone want their Ram target to get killed? 

Ram targetting has seemed off for me too. Maiming Stampede was going after my Rakka (usually hits Lydia) AFTER I had revived Lydia...  I don't know if it's related but I swear this past 2 weeks or so, the game has been acting strange. Weak Hits on NM Hydra seem to be 50% rate or higher and I'm failing, consistently, to land both debuffs for 2 debuff abilities on Chimera on NM with 500+ Acc and a Void champion.

I'm trying to uninstall and reinstall after clearing the cache.