Ok, first off: Some gladiator abilities are VERY useful for marauder. Don't be afraid to play with them.

Both are important, but something to note is that ALL left-side armor pieces have vitality on them regardless of class. And you use strength, just like pugilist and lancer. However, there IS a distinction between gear made for them, and gear made for tanks. Tank gear will have both physical and magical defense of an equal value that is significantly higher than other gear of the same item level. Most of the time this gear is restricted to only GLA, PLD, MRD, WAR, and DRK, though there are a few "tank oriented" pieces that are scalemail and allow LNC and DRG to use them, but they're far and few between, with most scale mail not having the defense of your heavy plate.

Crafting is not needed for endgame, though it's not TOO complicated once you learn the basics. Personally I like the freedom to make and repair my own stuff.