While I'm not entirely enthusiastic about the developer response here, posts like this are why they don't frequent the pvp forum. Merc DPS, while alive, is great. Lamenting a pve spec's performance in pvp is weird. Making mercs inexplicably immune to leap screws up 10 seperate ACs. And adding burst to a pve spec's damage will make them over-effective in operations.
What you're basically saying is "don't play Gunnery/Arsenal in PvP". Which is stupid. Every spec should have something to offer in PvP as the tree's description says "Damage", not "PvE". Watchman is probably the best DPS spec in PvE - it's also very, very effective in PvP. Certainly a lot more so than Gunnery. Snipers/Gunslingers also have three perfectly viable trees. Rage/Focus got buffed to make it better in PvE so now it's equally good in PvE and PvP as well.
I agree, however, that Gunnery/Arsenal doesn't need extra burst or leap immunity. A brief immunity to interrupts, for example, wouldn't affect PvE at all, neither would more escape abilities (which fit perfectly with the lore, btw: a Mercenary fights for money but his own life is more important than that; a Commando is an elite soldier who must be able to evaluate the situtation and know when to retreat).