By and large I'd say the "real" bosses are the ones you get Remembrances from (though that includes the Regal Ancestor Spirit, which was rather a forgettable whiff and a repeat). Which would be Godrick, Rennala, Radahn, Regal Ancestor Spirit, Fortissax, AStel, Rykard, Morgott, Fire Giant, Malenia, Mohg (real), Placidusax, Malekith, and Radagon/Elden Beast
The multi-enemies definitely seem poorly thought out. Catacomb dungeons in particular seem like a dumping ground for trash encounters shoved in a too small room (same with the couple of Ulcerated Tree spirits you fight in these rooms that the camera can't even handle them in)
With a bit more of solidly melee playthrough under my belt, yeah. I find I'm hitting an opening based on the AI RNGesusing up its mini-combo instead of its super mega chain. On both playthroughs I've noticed the AI with ranged moves will sit back and the second you touch a spell/bow/item that will plant you its fired its ranged move at you via input read. Or the hilarious rolliing based on input reads where you can be not even aimed at them or able to hit them.
And delayed attacks, well. Its been loitering in the series since DS2 at least. Along with the unnatural tracking (I've seen Leonine Misbegotten do a 170 degree turn in mid-leap during co-op). It does make the game look and often feel kind of garbage. Basically annihalating any sense of weight or momentum the games are usually lauded (though not by me) for.
The massive overtuning of boss hp is a weird one. Bleed basically becomes required as a percentage based output (with scarlet rot being the #2). With sorcery only keeping up because of the actual absurdity of that comet spell, and a weird tilt in the game to most things not resisting magic (conversely, something like 90% of the enemies resist holy damage, making the two spells that deal virtually ineffective. The final boss is even straight up healed by it). Which fits thematically in the lore oddly enough (though something like the red lightning or blackflame with lore implications should be equally hazardous) but makes for a total mismatch in the elemental outputs.
There is also the Melania specific issue. They gave the boss lifesteal. Even that channel that puts the bosses against each other using mods or whatever. Melania will always win because lifesteal, even eating 2 or 3 of Radahns comet tackles in the war of attrition. And its basically a doubled punishment on the player for any hit taken, as they both lose their health and restore hers. Which brings about to another problem across a large swathe of the enemies.... blocks and even parries still count as being hit and proc statuses. Which bleeds into PvP as well. Again giving a drastic overweighting to one style of build, even when contrasting monsters.