Stalkers have absolutly crappy health, absolutly crappy non-hidden damage, absolutly crappy defenses, absolutly crappy variety, and you want to take away the ability to one shot them?
Here's an idea. Find a defender with Tactics. Stick with him. Stalkers will die.
Just because they choose and kill a target doesn't mean they're overpowered... it means you need to find a team.
PVP Zones are not the arena. Find a team, and you will die less.