
Now before you all jump down my throat, I have not said anything about 1-on-1 combat, deathmatch etc. In these situations it is the ingenuity of the player that counts and the fantastical equipment they hold - a high level sorceror with the staff of the magi is indeed a powerful opponent.
But I have come to realise that, in the single player game, spellcasters are little more than an annoyance. Just look at the spell lists to see how every spell protection to make a spellcaster impregnable has another spell to take it down. Not only that but there are plenty of spells designed to disrupt and prevent spellcasting. To a party, in the single player game, spellcasters are nothing more than support. They are there to remove a hostile spellcaster's protections so fighters can take them down.
Again, just look at the plethora of weapons, equipment and methods non-spellcasters can use to chop up mages. Sure, mages can deal out their own damage but even when using beefed-up melee spells, they can't go toe-to-toe with a fighter. Summoned fodder? Fodder. Kill with spells? Just how many kills do your mages have copmared to your fighters. Again, support to weaken enemies/make them vulnerable to the fighters.
A part of the team, yes, but not the most crucial element. IMHO the only way to kill the really bad guys has always been to deal out lots of damage quickly, with melee weapons.
Priests are the better spellcasters. At least they can cast useful group spells and, with heavy armour and powerful melee weapons, mix it up in close quarters battle.
I will answer your mis-guided flames later.

PS How do you spellcasters deal with inherently magic-immune creatures like Rakshasas, Golems and Dragons?
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Its shocking, Foul. I was happily spamming away when BAM! a serious discussion broke out.