Companions are awesome, but most players end up getting an augment and just sticking with it. There is more the game could do.
1) Bolster per category could be increased to 25%, but base it on companion level instead of companion grade. Its the same thing except.. you would only gain the bolster for leveling the companion. (alternately, bolster could be a total of all up to 50%)
2) Add an artifact, item power, or gear stone that lets players bring an additional fighting companion, in exchange for -25% companion boost.
3) Add an artifact, item power, or gear stone that increases companion damage by 25% when there are no other companions nearby.
4) give us an option to designate which companion will be receiving our experience.