EP, if you run him as lead, really doesn't need any additional potency from mods. He gains 32% from that, bringing him to 79% already and anything >60% is more than enough for Arena (as your typical enemies will have no more than 75% tenacity).
Speed - you need your EP to go before your opponents EP. Unless you have a super fast Poe taunting first. Some health and defense primaries are useful so he can survive the first opponent barage.
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EP, if you run him as lead, really doesn't need any additional potency from mods. He gains 32% from that, bringing him to 79% already and anything >60% is more than enough for Arena (as your typical enemies will have no more than 75% tenacity).