How much hame time has he had in the 6 months prior to those 8 appearances? Not much i'd wager.
Strikers, all players really, need a run of hames to get match fit.
There are few strikers in the world than can not play for months at a time, and instantly start banging them in. Hogan will never be that good, but played regularly, he will score goals.
I can't recall him playing more than a few concurrent games since his arrival - often due to injury.
I think judging him on his time here is harsh. He's not great, he might not even be good, but at this level, given games, he is capable.