[SixOfSpades]

Berserker->Thief is a great setup if you want to build a strong Tank who can also slap on some good Leather armor and go stab somebody in the kidneys. You may also want to consider a Dwarven or Halfling Fighter/Thief for the same purpose, though: It's a tossup between whether you prefer the Berserker->Thief's immunities and Grandmastery, or the Fighter/Thief's THAC0 and Saving Throws.

When Dual-Classing, your weapon proficiencies DO NOT ADD. You cannot make a Cleric with * in Sling, then Dual to Mage and put a * in Sling, then magically get ** in Sling when your Cleric half reactivates. But this is a moot point in this case, since neither a Berserker nor a Thief can put more than a single star in a ranged weapon anyway.

To figure out the level at which you want to Dual, take the link in my sig, go to Appendix 1, and look up the EXP table. Take the EXP cap for the game you're playing, subtract the EXP needed to reach your Berserker level, and what's left will be the EXP you can invest in your Thief half. Figure the specifics out for yourself. It's not your character if you ask somebody else to design it for you.

F/M/Cs and F/M/Ts are generally held to suck, since they cannot reach 9th-level Wizard spells under the ToB cap, and for that reason they also never get any 10th-Level Wizard HLAs, thus severely handicapping their Mage component.

If you're planning a Berserker->Thief in order to choose UAI and swing Carsomyr, your Kensai->Thief can do that already. AND wear helms and gauntlets and armor.