I'll take a look at these later tonight.
Did you take lighting into account for these examples?
Yes, a Rogue could move out of a room (which seems to be your prefered modus operandi of acquiring superior cover in your explanations) and then back in. But the moment he moves into a well lit square (where many encounter squares in WotC material are lit) that does not have concealment or cover, he's no longer hiding.
As I mentioned, most of the chances to hide would only really be of use to someone who wanted to snipe from the shadows, or had the movement tricks to either flit from hiding into further cover, or come charging out of hiding onto the field.
But then, I don't see the issue with that. Staying hidden in the middle of the room or while sneaking up next to someone will often require special tricks or lightning.
The Barbarian absolutely can get to superior cover, then head back into an area of normal cover or concealment, and then come charging out of it.
For anyone who really wants lots of chances to hide in the midst of the room, there are items and powers and tricks that will let you set up areas of dim lightning and concealment. For a DM who wants more of those opportunities, he can simply design the encounters to have them!
If your objection is that the average WotC encounter does not have rooms where every PC can be stepping in and out of hiding on every turn... well, yes, you are correct. It might occasionally come up, but that
is rare. But most encounters have hiding available
somewhere. Some benefits certain styles more than others. But 'melee hiding' has never been something especially easy to do without actively designing a build around it, after all.