LVL 30, biotic maxed out, how to invest the remaining points?

Keep going and putting skills in all the areas. Theres a achievement for maxing them all out. Maybe some combat with the weapon you use first

Weapons, enough in the tech section to unlock team support and max that out, the combat support passive that gives you greater hover duration. Beyond that, just fill 'em in as you get 'em, your weapon damage will increase a small bit for each point you spend assuming you've spent points on the respective weapon types, so there's no reason not to spend points on unlocking combat powers even if you're never going to use them.

@sblantipodi In addition to the suggestions already made, you may want to try branching out into different skills, then start making some new builds. You can swap them in combat using the Favourites system.

Cheers. 

If you look at your passive powers you will note their effectiveness improves with the number of points invested in their speciality tree.  So if you want to play the Adept only game, putting points in skills you don't use indirectly increases the effectiveness of the skills you do use through the increase to your passives. However, before doing that I will suggest perhaps putting points into whatever your "Oh Sh!t" strategy is going to be.

Definetly invest into tech and soldier general passives (Team support, Combat fitness).

Also, boost the weapon you're using in combat section.

 The swap in combat is pretty messed up as all skills go into cool down, so I mainly pick three skills, and stay with them. other than the passives, I find little use in the other skills.

I do set up profiles, but there pretty useless, unless I swap to them before I enter combat.  ( I mean there not totally useless, but far less than what I would have imagined, because of the cool down )

   However after level 80 you begin to do so little damage, that it becomes pretty overwhelming, ( Like attacking an elephant with a Pea shooter, Even the trash mobs are a pain in the WA-zoo )