I understand what you are saying Nisch.

I've done minor multiboxing with a couple of melee (not running instances) and found that running through the mob with the tank and just waiting for the mob to settle then attacking worked wonders.

I'm trying to think of ways that Interact with and click to move would be superior.

I guess being able to send your team to a pesky caster that's broken out of CC and not been line of sighted whilst still tanking the main group might be nice.

I'm wondering if it will simplify some fights in violet hold - I'm thinking specifically of the boss where the orbs drop and only one toon can see them.
I was thinking a /target <name of orb things>
/target focustarget followed by the interact click would send the melee toon that can see them around dps ing them whilst everyone else
would continue on.

Or could you send one of your toons over to trigger the candles in violet hold if you are struggling.

I'm also thinking of fights like anomalus where you could send your team running to a spark then to the next one without having to drag them over with the tank.
(then again anomalus tends to go immune round about the same time so maybe not worth it).
Frost tombs on Prince Keleseth (although if everyone is on top of each other and put down aoe it's not too big a deal)

I'm not sure how useful all of the above would be, as I'm guessing there are work arounds for all of it.
I like the idea of it in principle, I'll have to see how it goes in practice when I actually get my melee team running instances.