So far the conclusion maybe you have found is to use Elemental Equilibrium+Storm Cloud and Explosive arrow in Path of Exile, so you always have a -50% resistance on targets with the fire explosion. But how to make an Explosive arrow build fun? Deadeye with Endless Munition for +1 projectile and +50% explosive radius? Elementalist with Elemental Proliferation on everything?
You’re better off using quill rain+a ring/abyss jewel with lightning or cold damage. Explosive arrow got hit extremely hard with the ignite nerfs, but if you are really set on trying to make a build around it, I’d suggest pathfinder if you have the poe currency for flasks, otherwise berserker for 40% more damage + warcry sustain or slayer for overkill leech+20% cull (equal to 25% more damage). Deadeye and elementalist are simply bad ascendancies right now, as other classes do their job but better.
Pathfinder and Ascendant are the best ascendancies right now. AOE is amazing and for single target you should abuse zerphi flask and possibly use a 4l setup for cremation for more single target. You can even run cremation in a 6L helm (conc effect + immolate in elder helm) and it basically solves your single target problems. Was able to take down all t16 guardians so far with this setup.
In fact, if you’re wanting to run EA, EA is an incredibly expensive skill. It’s not like most attacks. Each cast can cost 160~ mana per shot, needing 5 stacks, that’s 800 mana for one full stack. A lot of EA builds are forced into blood magic for this reason. Also note that your initial hit you’re not scaling, so don’t expect much leech action to take place. So yea, just be aware: with EA, you need to focus on being able to deal with the mana cost, you can’t just fudge it like you can with other attack and most spell builds.
Hopefully the above advice will be helpful to you, keep in mind that having enough orbs is important to you at any time in Path of Exile, orbs are what every exile needs in his backpack because these tiny round currency balls that can make you more powerful and effective in the game. And buy exalted orbs on U4GM will be a great choice for you.