This build is geared toward the use of his [Exalted Blade] and using it most of the time.

The umbra mods are great and [Excalibur] already has three formats to fit them so there is no reason to put them on.

having a great amount of duration, energy max and a little efficiency will allow you to keep [Exalted Blade] active for long period of time. According to my calculation, with efficiency and duration as it is right now, you use 17.5 energy to activate [Exalted Blade] and 1.13 energy per second while the ability is active. In theory, you can keep [Exalted Blade] active for 549 seconds if you use it at max energy.

[Augur Secrets] is optional for players and depends on their play style of type of mission. You can replace [Augur Secrets] for [Transient Fortitude] so you get more damage but at a loss of some duration which will affect how long the [Exalted Blade] can be kept for a period of time. Another option is [Blind Rage] where you get more strength but efficiency will be low and hard to use an ability without a constant source of energy.

[Steel Charge] is a great mod for [Excalibur] as his [Exalted Blade] will get the benefit and also give him more room to change mods. The 60% does not seem a lot but in the calculation, it does add up to a significant amount.