Balance trucks going to excavators

It always gets me that Ill have a large fleet and I need product moving, such as coal. I'm running 4 excavators and all of my random trucks like to pile up on one out of the 4. This happens all the time so while the other excavators are waiting for trucks, 1 has 6-8 at the other excavator?

Empty trucks should "wait" and pick an excavator only the moment an excavator needs a new truck, because current just became full. This issue becomes worse when combining small excavators with large trucks. An empty truck is waiting long time until an excavator fills up its current truck, at the same time another excavator is waiting for an empty truck.
Another consideration: could excavators "share" a truck, when digging close to each other?

I think two things should be guaranteed:
(1) There should not be more than 1 truck idling empty while waiting "behind" a truck being filled, glued to the same particular excavator.
(2) If there is an excavator waiting for a truck to become available with no truck on its way to that excavator, and there is a truck idling empty waiting at another excavator, then a truck should be redirected to the waiting excavator.
I like that trucks try to be ready for the excavator instead of waiting for the excavator to need them, but the current situation can create some ridiculous bottlenecks when one excavator gets a "harem" while the others starve.