Your on the right track. Keep farming those BH comms. Once you are able to start optimizing those BH pieces you want to aim for ~55% shield, ~55% absorb, 15-20% def. whatever HP's you have will be fine, not till Terror from beyond and NM EC do you need to start building those HP up. Mods and enhancements to look for are weighted or deflecting(I prefer the B models) for mods, bulwark, vigilant (both shield/absorb) or bastion, steadfast (shield/def) for enhancements. Plug augs in as you need to get specs in those ranges. Scrap any accuracy in favourite of any type of mitigation. Mitigation is the name of the game for PT tanks.
There's no reason to keep your defense that low. In my current gear (optimized 61s), I have about 56% shield, 55% absorb, 22.5% or so defense (with exotech stim) and about 24.5k hp. When my absorb relic procs I go up to a bit over 70% absorb, and the flame burst proc adds an another 8%.
None of the current content requires more hp than you get anyway while optimizing for mitigation, so there's no reason to ever choose endurance over any other defensive stat, unless you're an assassin.