Humphries looked very promising as a junior, in the 2014 u17 WC he averaged 19/11 with 3.3 bpg, including 41 and 19 with 5 blocks against Canada. So he was on the map early as an Australian prospect.
He's decently fluid as a 7 footer and he has very nice touch, but he's not much of an 'athlete', he's pretty grounded, not super long, etc.
Since going undrafted, he spent a solid year in the NBL (Aus league) and won ROY, he had a bad coach who probably mis/underutilized him though.
Since then, he's been working on expanding his range and getting in optimal shape. I don't think he's quite proven himself as a shooter just yet but the form is pretty solid and his great touch would be an encouraging indicator for shooting growth potential. Still has a long way to go though - hasn't cracked 70% FT yet and shot 33% from 3 in the G-League last season.
I haven't watched enough full games to make a fair comment on his defense, though I do find him to be a little soft, generally speaking.
His best showing was probably the G-League showcase where he scored 32 points.
I think there's Australian players that are better than him, but I think Isaac's getting a few of these NBA opportunities because of his youth and pedigree. This is reflected by the fact that other Australian bigs without NBA experience get gigs in the national team over him. He played a handful of minutes for Atlanta last season and this season, I think practicing with the Magic squad will be invaluable experience and hopefully help him grow as a player, because he is still young.
But as of right now, I think he'd be liability on an NBA court, so don't expect him playing any minutes for you guys, especially with the big depth you already have.