what rank do you have to be to be able to find a silthion queen or hive colony on your battle tab
also what rank do you have to be to see the Sha'din hypergrid and the Xiloy, Drannik Encephalon

I believe they are all 300+ although some of them have a cloak of 500 or so.

I can't really give you an answer, but...

A rank 300 Korteth crimson carrier is sharable down to 150 (per wiki).
A rank 250 Stalar command center is see-able at 150 (1st hand experience).

By that, I would guess that rank 400's would start to appear around 250-300.

I don't know what rank you are, but I hope this gives you something to compare to.

The Xiloy is down to 275, I would put it in the wiki but I forgot to check the maximum.

EDIT: I'm not positive, but I think the Silthion may not show up until after you do their mission chain. That could be wrong, but it would make sense. I was able to see them quite a while ago, maybe 250, maybe earlier, but I haven't actually found one myself.

yeah its after a chain of missions