It is a difficult one for sure since you can't solo the Drow Champions. i'm not sure what Jace's original logic was in restricting their drop rate, other than the fact that the Drow Blade Mage is otherwise very easy to access for what it drops. It is possible to go for another boss while you wait for the respawns, but when I did just that, I found players had to switch weapons (from Royal Sword to Sarin Trident to take on the Hornet Queen in the interim).
Before I take action though, there are some things to consider, like the Abstinok Key is sometimes dropped by the Locksmith, although that's more of a bonus than anything. However, I have one possible alternative (or coupled with an increase to the drop rate)... how would you feel if there were more Drow Champions in other locations, for example, a few spawning in the Subterranean City?
Adding spawns to Subterranean City seems worse in my opinion, since you either need characters in ttk already or a long trip to get there everytime...might as well just wait on the long spawn times of the 3 in sacred woods if thats the case. No one wants to farm the keys so this boss just doesn't get done very much for that reason.