RE: Large Rubs?
You can make mock rubs or scrapes but the key element is the deer must be using the area in the first place. I love seeing rubs but the really are only an indication to me of movement/activity. Here we see lots of rubs that are either along or the way(near) food sources, while a good indicator they really don't make me want to set up camp. Instead I start following them back in the transition area looking for a rubline with scrapes associated to it and I want to see rublines on either sides of the tree (meaning if travelling N/W I see rubs and when travelling S/E I also see rubs...this indicates a pattern of travel to the area beyond his bedroom). Once I find this I begin to get excited and thinking about how the deer is interacting within thearea. If this area offers safety I will hunt it, in the location that gives me as much advantage as possible. At this point I would place your mock techniques of scrapes, rubs, scent drips or rattling/calling, if you desire.
As to large based tree rubs, they can mean a big deer but don't assume!This season I witnessed a small buck working over fence posts andthen witnessed a larger buck beating the heck out of the saplings and small based poplars. I look for the hieght in which the branches are broken off above the rub itself for a better clue, but the only true way is witnessed. Like mentioned other deer will visit/use rubs and scrapes.
Best of luck!