Depends on the world, Corsicant has a central quest hub. the other worlds not so much, so people tend to see empty when there are the same number of people in their phase. I do think phases have artificially low limits, we have had more people online in my guild that some phases had players!
Of the three bots I know of, one is 43, the other two appear to have made 50 (I have not confirmed this but guild mates said they did) and I haven't seen them on again - however my weekday play is very very restrictive; like maybe an hour or two; so I will certainly miss them.
If you don't believe there are bots simply google the services offering them... its not a small list. I seriously doubt people are using them for the class quests - I would be impressed at that if someone could script it. All the ones I have seen merely are positioned to have access two multiple groups without drawing initial aggro.
iMac
2012-03-05 : The day SWTOR jumped the shark
Mages are basically "warlocks for girls" - Kerrath