Lets take another scenario,
You are defending a node alone, the sniper comes with some other class, lets say somebody with no stealth detection.
The other dude comes to node and starts capturing. The sniper position himself somewhat behind so he can have within his cone of vision his team mate (if you will try to mezz the guy doing the captures, you will be in sniper's vision cone).
The sniper rolls into cover, and starts gaining stealth detection levels, he might as well activate entrench. The other dude is capturing.
What is your plan to delay the capture for as long as possible? Do you seek to sleep the sniper before he gets to cover? when will you use sneak?
My gut instinct in situations like this is always to sleep the non-Sniper and take my chances against the Sniper himself; there are few classes I would rather fight in a 1v1. Maybe a Lightning Sorc, but that's about it. If the Sniper doesn't have his Escape up, we can hit him a lot harder than we can his friend in the first few seconds of our opener. Also, with the PTS changes to Guard, damage dealt to the guarded target will no longer crack a mezz on the guard himself. That gives us better defensive options.
The other problem here is that the Sniper might have a stealther with him. If he does, you do not want to go out and meet the Sniper to sap; the enemy stealther might have detection talents and/or sneak/fadeout up, which can put you in a vulnerable position by rushing out to meet a supposedly "solo" attacker. I generally hide as long as possible just to confirm how many opponents are around.
Let's assume that the Sniper is watching the node capper. If the Sniper is himself capping a node with (maybe) Sin/Op backup, that's another scenario entirely.
So if the Sniper is watching the node with his detection, my objective is to Sleep Dart his buddy before opening on the Sniper. That means I need to reach the capper without getting detected.
Thankfully, and this is a purely geometric and theoretical model, I do not think there is ANYWHERE that the Sniper can stand where I cannot navigate around his cone to Sleep Dart his buddy. If he stands too close to the capper, I just approach the sniper from behind and Dart over his shoulder. If he stands too far away from the capper, I just approach from the front, interposing the node between myself and the Sniper. This is a very tricky thing to model out, but I think the approach would always be clear.