After the March QoL Update, Deerclops does 120 damage to both mobs and players while it was 75 to players and 150 to mobs.
First I thought this as an intended feature but Winter's Feast event Deerclops's laser attack does 60 against player and 120 against mobs, so it looks like just a bug which Deerclops's PvE/PvP damage difference isn't working correctly.
This is the footage that shows this bug; the sweep attack does 120 damage to both players and mobs, while laser attack does 60 to players and 120 to mobs.
Deerclops's sweep attack does same 120 damage to both mobs and players, while Winter's Feast version laser attack does not. (They should deal exactly the same damage)