"forget about a skill like that, it's more than impossible"
is on to something. Don't dismiss it so easily just because it doesn't sound as fun as AR-DS. Think about it, Lion's are gunners, they should have a larger variety of gun-skills which include sniping from longer distances than we're used to. Think about it for a second-- they're doing to nerf this 10-shot someway. It might be a long-cast time like Mana Arrow/AR. It might be a long cool-time. It might take as long as shield breaker to cast. So considering all this will it even be any use against bunnies with skills like flash-cut that utilize dash? While you're getting off your 10 shots what says a bunny isn't going to run up and smash your brains out? A lot of good bunnies have enough HP to tank a few shots even without guard. And in all likelyness this skill is never going to happen.
The best way to combat guard is pretty much combo and run. And even then it only works until you get hit. I can achieve about 20k HP and decent AC and unless the guard buffy/bunny can onehit me I can take out guard with a lot of pot-spamming. (Did it earlier while messing with my friend's buffalo-- ended up with getting shock-vibed whenever I walked into the map. ;-; )
And as far as SoH goes I've only killed one Light-Mage I wasn't testing on. (This is back when I had been getting ganged by a couple recently advanced bunnies and a mid-level buffalo.) Shield Breaker works only that it increases the amount of damage the shield takes,(I suppose that's rather obvious seeing as the skill lowers DP) rather than reducing the MA/Shield HP like Magic Meltdown does. Honestly though-- the best weapon against L-Mages is a charm with Magic Meltdown. (Dark Mages are rather easily hunted by us gunners. :B)
Gunners still have their place in PVP/GVG, it's just a matter of finding out what works for your character. Get good AC, moderate LK, good HP, Combo Well? Take a charm or not-scarily haxed power or two on for size. Get Moderate to good AC, Great LK, Moderate HP, Combo well? Take a mage or two on for size. Can't combo well? Fall back and support, of course this is talking more towards GVG now, or work on it. And even if you're just there to whoaar off aura or be the item-girl, you've still got a place in the team even if it's ghetto-medic.
I feel like I have no idea wdf I'm talking about.