the main thing to keep in mind with hive mind is movement tbh, the first phase those blobs only have a certain range so you can exploit that and pop in quickly to ensure the hive mind doesn't despawn, the second phase is like skeletron, you can't get hit otherwise you just get stunlocked into oblivion, basically all you should really be getting hit by are blobs occasionally and maybe those projectiles otherwise you just need to git gud :^)
"Like Skeletron" ... eh, Skeletron doesn't stun-lock you to death if you get hit by it... unless you are talking about Expert Skeletron?
I don't do Expert, so I wouldn't know. But then I don't expect a boss in Non-Expert to act like other (vanilla) bosses in Expert. I mean, seriously, what is it with the Dark Souls crowd who think we need that kind of stuff going on in Non-Expert?
If you want Expert Challenge, hey awesome, click the Expert option when you make your world. But do you need to force that on players who want to play on Normal mode, too?
And it isn't just about "Git Gud", it's about the thing being overtuned compared to bosses you fight before and after it.
Hive Mind is supposed to be the Corruption variant of the Brain of Cthulhu, and like the BoC, it likes to teleport ontop of you and does some rather good damage. However, the BoC's second form does not have adds, nor does it have
three types of projectiles, nor does it do 40 damage a pop. It does more like 20-25 damage per hit, non-Expert.
The Hive Mind, however has three different adds that spawn in its second phase (the blobs, the spiked blobs, AND the hearts that rain down on you which I feel is just overkill) and it's fought at a point in the game where, if you're not overgearing encounters, you do not have very many AoE-heavy weapons, and since it is meant to be fought (supposedly) before Skeletron, you don't even have KB immunity, and KB is most of what KILLS you in this fight. You get hit ONCE by the thing, and you're going to lose 50%+ of your health because it stunlocks you and there is pretty much zero escape.
At least, with the Brain of Cthulhu, you could keep it at bay with the Rotted Fork or any Yo-Yo but you could still get killed if certain conditions happen even with those two weapons.
This thing, though, pretty much you have to pray you get lucky with its RNG teleports, or simply wait until you have a Cobalt/Obsidian Shield and better weapons to kill the junk with. Oh, and might I add that the adds the Hive Mind spawns are... 1). Twice as tanky as BoC's, and 2). Move twice as fast as BoC's, and 3). The Hearts rain a projectile down on top of you. Oh, and 4). The blobs also shoot at you, which the Hive Mind Itself also does in its 2nd Phase.
It's just simply overtuned for the point you're supposedly supposed to fight the thing during the game. The player just does not have the tools to properly deal with this fight at that point, and overgearing it is the only feasible way of defeating it unless you're an Expert player.
But... if I were an Expert Player,
I would be playing on on Expert.
EDIT: And sure, beating it overgeared is an option, but the rewards from its drops are already obsolete which means there's not much reason to fight the boss whatsoever, which makes it a pointless boss unless you need to farm it for the crafting material it drops, in which case you'd just come back with hardmode weapons and roflstomp it.
EDIT2: The boss after it (Slime God) is 3x easier as long as you made a pair of wings (which is within the progression, no sequence breaking required) and prepared a decent sized portion of the world (or were careful about where you summon it). I was able to kill Slime God while barely even getting hit whatsoever. That's another clear indicator a boss is overtuned, when it is more difficult than other bosses later in the progression. And the boss before it is such a pushover, that it isn't even worth mentioning.