While you can currently get an unbounded Intelligence on the Level Up page, it's effectiveness is still capped. Gedan's been going through bug reports, and that's on the first page. Maybe it will get fixed.
Tech is probably best, simply because they get Intelligence to everything.
Smuggler does get 1/2 Intelligence as bonus Sneak Attack/Aim damage.
Mercenary is the worst, because they only have one ability that relies on Intelligence.
