-helmets? use IOUN Stones, problem solved
Hardly. There are many helms that are considerably more useful than any ioun stone. One of them - the Helm of Balduran - you can pick up at the very beginning of BG2. There's also Vhailor's Helm, Helm of Glory and lots of others. Just because you can put -something- in the slot - and every ioun stone before TOB is really really really really crappy - doesn't mean "problem solved".
-gauntlets? well this is a disadvantage indeed
Indeed. And note that that includes bracers. Bad news for a mage, dontchaknow.
And I forgot to mention the "no missile weapons" thing, too. Pretty big one there.
Also, the bonuses that kensai get can be mostly duplicated by the berzerker's rage
No they aren't mostly duplicated. You might get half the bonuses the kensai has all the time (if you dual the kensai at 13, when you dual later it should be even less), and you get them for the duration of the rage and after that you suffer penalties. If memory serves rage gives also AC penalty?
Who the hell duals -after- 13? You'd have to get to at least 15 to increase kensai bonuses beyond what you get at 12... do that, and you'll get maybe 30 minutes at the end of TOB with both classes activated.
The main argument of when to dual is between 9, 12 and 13. Now, a kensai dualing at 12 or 13 gets +4 THACO and -2 AC. A berserker raged gets +2 THACO and -2 AC. Yeah, I think that qualifies as "mostly duplicated". If you dual at level 9, as many people do, it's even closer, only a one point THACO difference. At any rate, the rage bonuses are equal or BETTER than kensai bonuses at every level up to 9 (which means all of BG1 and some of BG2, if you're playing with TuTu or BGT).
If memory serves rage gives also AC penalty?
No, it gives a 2 AC -bonus-. You only get the AC and THACO penalties after the rage has worn off, but it's very brief. The thing is, you have the bonuses you need for the tough fights, when you need them. What, were you -not- planning on resting immediately after fighting that dragon anyway?
So here come the first real advantages.
Yes, "first", assuming helms, bracers and missile weapons don't count at all.
This stuff is useful early on before you have a cleric with chaotic commands spell, or if you solo. After you reactivated your fighter class it's of no significance anymore, except Maze & Imprisonment. Who attacks you with these spells? Some liches and the Elder Orbs/Hive mother sometimes.
Yes. It is helpful in a majority of those fights that are -actually difficult- to begin with. I don't see a huge lot of gain in getting bonuses for easy fights that you'll blow through and have no problem hitting the targets anyway. The toughest fights in the game involve elder orbs and liches frequently. You can use rage more often than you'll ever actually need to.
Oh, and by the way? Chaotic Commands doesn't help against being Stunned, either. Rage does.
Btw does Rage protect from these beholder rays that maze or imprison you?
Yes.
Minsks rage at least didn't protect him (in my games) or has he a different kind of rage?
His is different. Although, I did think it protected him too. Weird.
So the difference is HUGE in MANY fights. I say the difference is negligible for the majority of the game. the only time rage really comes in handy is vs Beholders with their anti-magic rays.
"The majority of the game" would actually be that portion of the game where you have NOT reactivated your mage abilities, and Spell Immunity: Abjuration isn't available to you. Rage really is available for "the majority of the game". Your work arounds for your kensai aren't.
You really seem to consider trivial fights to, like, really matter. To me, it is perfectly fair to say "MANY" fights, and that they make a "HUGE" difference, because they are useful in many -actually difficult- fights. Trivial fights don't matter.
Also, your solutions require a lot of pre-buffing before fights, Chaotic Commands and Immunity and so forth. Berserker's much more convenient, just rage-and-go. And the berserker can use those spell slots for better purposes. Mage level 5 spell slots are pretty valuable all the way to the endgame due to Breach and Spell Shield.
Qwinn