Vigor is really kinda necessary for a stamblade. Getting there takes about 85,000 AP all together. That's a bit...but consider it used to be like 800,000 AP. Barf. Anyway, you can get your 85,000 without doing much player fighting.

The least battle-intensive way involves some gold - repair walls. At 60 AP per repair, it takes about 1400 repairs, and at 90 gold per kit that's 125,000 gold. During busy times, go to the keeps on the sides of the map when your team owns them. There's almost always 2,000 AP worth of repairs at these keeps.

Another way is to assist in keep defense. Defense actually pays out tons of AP. Go to where big battles keep occurring. Help out with siege engines or repairs or heals. Feel free to hang back in the inner keep. If your team wins, stick around for a few thousand AP. If the keep is lost, just let the enemy kill you and then go find another defense game.

The third is to do the repeatable billboard quests...resource captures, scouting, etc. Go into an empty server where your team owns a good bit of the map, then do two or three scouts and a couple of resource captures. (With update 13, resource capture will be increased to 1,000 AP).

Using a combo of these, you can earn vigor on a character in four or five cyrodiil sessions, and barely ever fight another human. Commit...your nightblade will thank you.