The Nightstalker didn't work out for me in PvP. I might have liked if it instantly cancelled other supers but it's just so underwhelming. I've moved onto building my Defender Titan now and that's a sub-class I fell in love with instantly and I'm only half way through the perk tree! I can't believe I haven't tried this sooner.
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If you love to be the support guy, Defender is just frickin' awesome.