the hazmat pummeler mk2 ear is BiS.. for hazmat implants, it depends on what your other stats are, as well as whether you run watchman or combat.
for combat
1. keep 100% melee accuracy (anything higher is wasteful and better served elsewhere even if you're into DR)
2. crit rating anywhere from 150-328
3. max out power
4. surge will naturally be well in DR with the way current mods/enh are made. (there are no power/crit enh, there are only power/acc and power/surge)
you'll find as you min/max your gear,
1. all your mods should be Advanced Deft 27 (56str/44power)
2. your enhancements will force you to choose between power and crit . surge comes with both of these and you'll be well into diminishing returns with BiS
3. if you pick power, then you have 2 enh to choose from: power/surge and power/accuracy
it may seem that the hazmat implants are downgrades, since there are none that have high str and power. however, you'll find that they are BiS is if you can meet the minimum requirements for crit and accuracy with the implants and stock up on power enhancements instead.
e.g. ataru form with 3 points into the accuracy talent (for PVE, the points are not better spent elsewhere) and str augments
2 Hazmat Pummeler MK-1 implants: 76 crit/60 acc will yield:
accuracy rating 120 = 101.13%
cirt rating 152 = melee crit 30.86% (with exotech stim, full raid buffs)
+6 str&end over BH implants, 12/12 with 2
with just these 2 implants, all the enhancements can be adept mod 27 (44power/60surge) with:
1008 power & 79.44% crit multiplier
for watchman, you lose the buff to accuracy from ataru, so gearing is a bit different
sidenote:
if you've already purchased a different Hazmat implant, i.e. the crit/surge one, don't worry. you can just swap in 2 44power/60acc enh for an equivalent setup.