Elurian

BA pairs well with bio or stone. Both boost damage and augment BA's solid offensive abilities; stone has 2 damage boosters, one of which is a DoT that can often finish nearly dead foes without having to waste another heavy axe attack. The extra recharge Force Feedback enhancement in knockdown attacks (which BA has a ton of) brings your bio clickies back faster, which is huge defensively. Stone is a solid defense oriented set, soft-cappable by scrappers, with a reasonable amount of regen, HP boost, minor recharge and recovery boosts (both of which BA needs help with); as a set, I like Stone on scrappers best.

Battle Axe/Stone. BA is pretty consistently supported by data as one of the top 3-4 DPA sets in both ST and AOE, and it has Knockdown and defense debuff, which are great on their own and also bring the ability to slot for chance to recharge and resist debuff. Stone Armor is badly slept on for scrappers. It can add almost as much damage as bio, is much easier to softcap, has a good resist foundation on top of that, is one of the few sets with no psi hole, brings solid healing and regen even without the T9 Geode and basically no downtime with Geode. A recent poll had bio at ~8x as popular as stone, and it is probably stronger against moderate or weak content or for very short periods against hard content, because of the absorbs, but if you are soloing a variety of hard content consistently, stone is arguably a stronger set that is massively underrated - especially on a scrapper. Bio and stone are both excellent sets for all ATs, but after a lot of experimentation with the 2 armor sets, I like bio more on a tanker and stone on a scrapper (though bio does benefit a lot from the potential recharge synergy with BA).