About strength and dex cross-classing - I find they benefit the most from picking up other class skills. Unlike a mage, where having more spells only increases versatility, more CD talents is a multiplication of the dmg output. Warrior/Barb absolutely love to get the active talents from each other. If you get shields up, power strike, cyclone strike and charge you can keep cycling them for huge damage output. Take a few duelist talents as well, always strong! Rogue/Ranger abilities also complement each other perfectly and are a massive power multiplier. Perfect aim, power shot, bear trap, sleep bomb? The things you can do with those are downright unfair to the enemies haha.
Freeze/dominate are just broken, don't compare anything to that xD