Yeah, they should have never ever EVER given Clan weapons +damage on top of every other tech buff they got.
Endo/FF, XL engines, built in CASE (one more crit and half ton of mass), many of the heavier weapons being substantially lighter/smaller than IS counterparts. All bad enough.
But then you get to range and damage output and it gets stupid.
Clan ER medium laser weighs one ton, takes one crit slot, and deals seven damage, with a range of 5/10/15, generating 5 heat.
The IS ER medium laser weighs the same, same crit space, deals five damage, with a range of 4/8/12, generating same heat.
This means the Clan ER medium is damned near on par with the IS large laser. For one less point of damage, you generate three less heat, hit at the same range, only take up one crit as opposed to two and it weighs 20 percent of what a large laser does.
Pulse lasers are even worse. IS pulse lasers are, in my opinion, generally balanced as they give a VERY modest damage boost (+1) and a solid to-hit bonus (-2) for losing about 33% of their range.
But the Clan medium pulse laser has 4/8/12 range, one crit, 2 tons, and deals 7 damage for four heat. Meanwhile, the IS medium pulse laser is practically a close-quarters weapon, with a 2/4/6 range, dealing 6 damage for four heat, same crit/weight.
It's REALLY noticeable with the large pulse laser. The poor IS LPL plods along, generating 10 heat for 9 damage, with a 3/7/10 range -- barely better than a stock medium laser, while weighing 7 tons and taking 2 crit slots.
The Clan LPL, by comparison, is broken as fuck. 10 damage, 10 heat, six tons, 2 crits... and an ungodly 6/14/20 range. Don't forget the -2 to hit bonus from pulse, which nudges the dice substantially in your favor when shooting at medium/long ranges or at fast targets.