My BH is 38lvl now and I have lvl'd entirely as a Pyrotech. I did try Arsenal at one point and wasn't comfortable with it, so I respecced back to PvP Pyro tree.
I do use Mako for almost everything. In PvE I am highly successful at any type of mob, and rarely die, in fact when most elites fall dead at my feet, a lot of times I am still just under full health, yes I apply my CD's, but even with CD's ramping down, I have no reservation about pulling another Elite.
Another fact, many mobs I solo becuase I sent Mako away to sell my grey items, I might not kill elites without a companion out, but trash mobs are doable with better than average gear. At 38lvl I am right around 9500 health or more with just natural buff, no stims.
If Arsenal is so much better, then my loss I guess, I wanted to do more than spam Tracer Missile.
What I do wonder about is the healing tree, I would like to give that a shot someday and see how well it does. Any info on Heal tree would be greatly appreciated. Wish there was a dual spec arrangement in the game, maybe at some point in the future.