With healing companions not really healing and fighting companions not really fighting, the answer is clearly an augment - but which augment?
One answer is
- For BiS gear, you want a legendary Deepcrow Hatchling anyhow for an offensive slot for the +8000 Power bonus, so why not make it do double duty and use it as summoned as well?
The Deepcrow Hatchling gives a special bonus to Critical Strike, Deflect and Awareness, so if you are below cap on any of those stats, fine. However, if you have capped those and cost is not really an issue, you would be looking at using a different augment companions as summoned - one that gives a special bonus to Power.
- Bulette Pup (Power, Defense, CA)
- Star of Simril (Power, Crit Avoidance, Awareness)
- Quasit (Power, Defense, Accuracy)
- Polar Bear Cub (Power, Critical Strike, Awareness)
If you have reached "maximum efficiency" for all the stats, it really doesn't matter which one you use, but otherwise what is "best" really comes down to which stats you are lacking. In my case the best active augment would be either Bulette Pup (CA not maxed) or Star of Simril (Crit Avoidance not maxed). I already have the other stats maxed, so Quasit and Polar bear cub would not be as good for me.