This build is designed for jumping to one enemy, emptying its life bar, and when he attempts to escape, then you switch to the Mercurry Cannon and give them the final blow. Atma's Impailer combined with health items gives you both durability and attack damage, so even if you can't reach an enemy, you can still push him till your team comes to help.
You can also purchase Health Pots. That way, you can stay for more time in battle. Don't worry about your mana; it refills with each basic attack of the Mercury Hammer because of Lightining Field's Passive.