I have now finally made a group with F/M and I have to roll back on my previous statement.
F/M cannot replace a Sorcerer or a pure Mage or a dualclass Mage. They simply need 6 million xp to get to level 9 spells while Sorcerer and Mage are already there at 3 mio xp. And dualclass Mage, well, that depends, a Swashbuckler(10) is there very quickly (160,000 xp for Thief 10), a Berserker or Kensai (13) / Mage would still take its time (1.25 Mio xp for Fighter 13).
And you have to pick the spells on the F/M to support the Fighter, not to be actually a main caster.
If you play BP straight you will end up with 6 mio xp, so thats when you finally get level 9 spells. Thats too late.
I also regret that I didnt made a Gnome Fighter/Illusionist. I just dont need any Necromancy on my F/M in the first place. The extra spell per spell level would be great, and even much more importantly the better saves of Gnomes would be uber.
I would still miss the great saves on death as well, but in many cases against spells would have already sufficed.
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Cleric/Mage is a whole different matter. They have SO MANY SPELLS. They are kind of lowlevel though, they too take 6 mio xp to finally get to level 9. But so many tricks are possible all of a sudden that havent been before. For example in the fight against the demons, I simply set up a Contingency "on enemy sighted cast Protection from Evil 10' Radius" on my C/M and for the first time ever this battle felt controllable and not like total chaos.
And yes I've cast Protection from Evil 10' Radius in this battle before, all the time, but this time it actually was in time to stop most attacks so I had time to buff my group before attacking.
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Zaxares: - Elven Archer (This character actually wound up being my primary damage dealer by far. Archers are downright INSANE.)
Try: Dwarven Barbarian, Str 18/nn, 2 points Axe, 2 points dualwiedling, then 2 points Hammer duing levelup, then probably a twohanded weapon of choice for Whirlwind attacks; I always pick Halberd.
Gets Str 22 during rage, thats +10 damage on every attack, and thats before strength girdles.
AND the guy can tank, with enormous hitpoints and later physical resistance.
AND has awesome saving throws.
AND thanks to his extra runspeed is excellent at kite tanking, too.
Archers are IMHO for archery fans alone. Objectively they are just dead boring. And amazingly squishy when targeted by enemies.
Granted, warriors are in general quite boring in AD&D. But Barbarian is one of the most fun ones.
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By the way the highest damage output I've seen on any warrior class was Berserker(13)/Cleric.
With the spell level 5 priest spell Righteous Magic they get up to +6 on strength and deal maximum damage with every attack.
With strength 18/nn to start and the Ring they get for level 25 Cleric (+1 strength, among other things) they reach strength 25 without any strength items.
With dualwielding and 5 points in the main hand weapon type they get 4 attacks; with Improved Haste thats 8 attacks. Who needs Whirlwinds anymore ? Granted there is this Spear +3 with +10 extra damage, and theres of course Vorpal weapons etc.
But yes they are classic glas cannons. If they cannot hide behind great tanks anymore they suddenly die a lot. All they can get is 25% damage reduction from Armor of Faith.