A single encounter involving 15 goblins all with different HPs sounds like a massive headache for the DM and players.
However, having a first combat with goblins all at 7HP, and then (X sessions or levels later) having another combat with goblins all at 10 or 12 HP, representing "elite goblins," is perfectly in line with the rules and an easy change the DM can make for more difficult encounters.
It’s easy to talk about HP and forgetting to talk about the AC 10 instead of 15 and how that damage the spell efficiency balance. Again, this is not about a problem generated by a single homebrew. It’s the problem generated by a combination of them. Elite goblins should have even higher AC by your terms (16 would do just fine)