This build should take you to level cap pretty easily. It's a balance of strength and efficiency, and should let you keep your energy permanently maxed while mowing down everyone in your path. Also I threw in Rolling Guard because it's the best survivability mod in the game.
A small note about using Equilibrium, it's pretty much required to use Synth Fiber on your companion to make sure that you can always pick up health orbs. That lets us keep topped up on energy at all times.

This build is meant for shield gating without relying on augur mods, so we can't have efficiency more than 100%. This allows us to fill our shields completely on a single cast of Sonar. Obviously a decaying dragon key is needed here.

At first glance, the power on this build may seem lacking, with the conditionals we can get very high multipliers. This build is meant to be used with Zenurik and at least a few Crimson Archon Shards in order to get us to the 95% slow on Gloom. (I went 2 crimson 3 amber on my Banshee to boost the casting speed)

The math works out like this - Base Strength: 144 + Energy Conversion: 50 + Molt Augmented: 60 + Zenurik circle: 20 + 2 Archon Shards: 30 = 304 Strength

This number gets us well above the 95% slow cap without having to worry about duration or efficiency tradeoffs from corrupted mods. It can be a little difficult managing all the conditionals, and you will have to "level up" your gloom as you go through missions in order to hit max slow %. I generally cast gloom at the beginning of the mission with the zenurik circle modifier, and when I get my first energy orb I cast it again to take advantage of the +50 strength. Then I just chill until I hit a high modifier with Molt Augmented and I cast for a final time. With the two archon shards, you will easily pass the slow cap and you won't have to worry about recasting unless you enter a nullifier field.

Because of the conditional nature of this build's strength, you won't always have an outrageously high sonar multiplier. This is fine however, because sonar is just that good. Your sonar multiplier will bounce between about 8.5x and 14.2x depending on the active conditionals, which is fine even for level cap. I wouldn't bother actively trying to plan your sonar casts to maximize bonuses; just let it all happen naturally and you'll still get high multipliers due to the large numbers of energy orbs in SP missions.

As one last note, the eximus slot isn't really important. I have Primed Sure Footed but you can use anything that you want.

I think I hit all the main points, but leave a comment if you have any questions about the build.