Cloak gives a shift of 3 to the cloaked ship, it does not show up on the display.. using ECCM at 6 poionts power will negate 2 of the shift, that is if the cloaking ship is not using ECM itself...
Now a cloaked ship can have a net of 5 shift if using 6 points power in ECM, and can even get to 8 shift us also using Eratic Manuvers (but giving the cloaked ship a - 3 shift to hit.. but since it is cloaked, that is cancelled out with the inability for fire anyways..
as such, it is hard to get Direct Fire heavy weapons to actually hit when they are hard pressed to hit anyways.. take Photons.. Normal Torps will miss 1 in 4 at range 4 with 0 shift... with a 2 shift, maybe 1 torp in 4 will hit at range 4, and that is only a 68% chance of doing so.. forget it with a cloaked ship and torps.. you may get 1 in 25 to hit at range 0 with ECCM at 6 on a cloaked ship using ECM...
it is not a bug, it is game design..
And even if the weapon hits.. the damage bracket is 33% chance for full damage, 33% chance for 1/2 damage and 33% chance for 1/4 damage....needless to say your shooting at the wind and hoping to hurt it.