Countering snipers isn't difficult once you realise that most players can't snipe very well and rely on lining up with choke points via pretty obvious lanes. If you absolutely need to go through the lane, slide, blink or jump so that you're not at head level. Most players will either miss or body shot you and then you're out of their sight line. I'm far from an amazing player (especially in Trials) but I rarely die to snipers unless I'm a) ignoring my own advice or b) playing against people who can stay mobile whilst sniping and can hit some great shots from unexpected angles. The added bonus of lots of terrible snipers is the sheer number of kills I get from people who try to quick scope or no scope me when I push with a primary. Most of them would have actually won the engagement if they'd had their -blam!-ing primary out in the first place! Oh, and people tunnel visioning so hard that they don't notice me hitting them from the side with a shotgun. Pantheon is a great map for this!