Str/Int is perfectly fine as a hybrid, although I can't personally voice for the two-handed version. All I have to say is that investing in the Shield ability, combined with the Strength to equip shields, is actually very good for a melee caster type and allows ability points to partially replace the attribute points not put in Con; plus, the Man-at-arms talents are very strong, and some of the skills aren't half bad either.
I also believe that Dex/Int with Bow, Quickdraw (Expert Marksman 5) and some spells could also be pretty good, providing the spells chosen don't mimic the effects of special arrows. Also, Str/Dex melee with a dagger and a shield (as I said earlier, shields are good) should be viable.
The trick to these classes is understanding one thing: most of the time, your hybrid isn't going to use spells for damage, because that's what the weapon is for. For a hybrid, spells are more about controlling the battle through inflicting status effects and providing boosts to other party members. For example, if you're using a big two-handed weapon, you will get more utility out of a skill like Shocking Touch than you will out of Small Fireball. Another example: my Str/Int starts a lot of fights off with 7 AP spent on Rain, then Bitter Cold to freeze something; later on, of course, he's charging in there with Battering Ram and thwacking things to death, and he's very good at tanking thanks to Picture of Health and his trusty shield, something Jahan (my pure caster) can't claim.
