In my opinion, the best party in Might & Magic is one composed of similar characters. Specifically, in Might & Magic 8: if it's a melee party, then 3 trolls + a knight + a dragon (moving too slowly on the ground, it's better to fly). If it's a mage party, then 4 necromancers and again a dragon (you can also take a dark elf instead of one of the necromancers).

In this case, it will be monotonous and boring during the playthrough - that's one thing. Secondly, the melee party mentioned will be assembled without buffs and healing (a minotaur is not a panacea), and the mage party will struggle with monsters that have high magic resistance.

A party like warrior, mage, thief/archer, cleric, dragon - this is a party that won't do much in melee combat (the cleric and necromancer will go down quickly), and in ranged combat, the warrior and cleric aren't very useful. In general, such a party can do everything except fight effectively.

A proper cleric doesn't go down in melee combat (and I don't need you to prove otherwise; about 70% of my Might & Magic playthroughs were with a cleric), and the necromancer's task isn't to fight in melee, but to damage the enemies as much as possible while the party reaches them, and then let him faint - the cleric heals. You're wrong about the cleric in ranged combat - Flying Fist is great, and on an open map, Sunbeam incinerates everything.
Thus, in a melee party, one is weak (the necromancer), and in ranged combat, one is weak - the knight. And in homogeneous parties, either everyone will suffer while they reach the enemy (melee party), or a melee monster that flanks will eat the entire party (mage party).

Might & Magic isn't an MMORPG like Lineage 2, where you need to have buffers, melee fighters, archers, and mages for serious battles.

Fighter, cleric, thief, and mage - this is the basic skeleton of a party not only in MMORPGs. If I remember correctly, their victorious march began with D&D, which was long before the advent of PCs in general and MMORPGs in particular. And MMORPGs, not during "Guild Wars," but at level, are not much different from ordinary RPGs, except that you have to control one character instead of all of them.