So what is the majority opinion on the best class to play through on Normal Difficulty? I figure once I beat it once I'll switch to a different specialization on HARD to keep the game fresh.

Right now I'm at Level 7 and can't decide what to pick. I'm leaning towards Alchemy.

I played through as Sword Mastery on normal for the first play through, combat was laughably easy when I hit chapter 2.

I just started a new game on Hard and plan on going full Alchemy, as it seems to be the most challenging.

Frankly, no matter what specialty you pick, you'll end up fighting with your sword most of the time, so I'd guess swordfighting is the most powerful choice.

Still, I'd guess you can beat normal with any of the three. I personally picked magic, and had relatively little trouble finishing the game even though none of the signs are effective against the last (compulsory) boss.
From what I saw of the trees, though, apart from the ability giving bonus damage to bombs and traps, most of the alchemy abilities seem rather underpowered. Then again, I very rarely used alchemy during the game (except for the swallow potion) so maybe I'm underestimating its usefulness.