Do they really have worst dps, heals, and awful in pvp.
First off, it's important to note that BHs are not an appropriate category for comparison: Mercs and Powertechs are *vastly* different and have wildly different levels of effectiveness in both PvP and PvE.
For PvP, Mercs are generally considered almost worthless: they have terrible mobility and no turret protections coupled with mediocre survivability thanks to only having a single real survivability CD. For PvE, however, Mercs are simply stellar: mobility matters much less so their need to stand and constantly cast to deal damage isn't really a major detraction. As PvE healers, they are *marginally* sub-par compared to the others, but it's not a substantial concern: Commandos are bad healers in the same vein that Guardians are bad tanks (they're worse than the others, but by such a small degree that the player makes a *way* bigger difference than the class itself).
Powertechs, on the other hand, are rarely considered bad: Pyrotech PTs compete for the best PvE DPS coupled with *amazing* burst damage that makes them stellar at PvP, especially when coupled with Harpoon; AP PTs get a bad rap but can be quite effective in both PvE and PvP (they'll have less damage in PvP, but more utility and survivability; in PvE, they deal roughly similar DPS, but they're way more complicated to play than Pyro so they're not nearly as popular). PT tanks are only derided as being the "simple" tanks because they're almost impossible to screw up, but their performance is perfectly acceptable when compared to the other tanks; their simplicity should, honestly, be considered an advantage because it allows most players to focus more readily on stuff *other* than what buttons to press. The only time a Powertech is generally going to be considered not valuable is as a PvP tank: Shield Tech just isn't particularly useful in PvP thanks to the fact that a massive number of player attacks bypass shield and defense chance and PTs just don't have the same amount of utility that the other tanks bring.
In short, you're kinda right but mostly wrong. Mercs are the "bad in PvP" AC, but BHs, as a whole, are perfectly functional and effective in every other way.