So thieves, as a collective, are not the problem it seems. Certain parts of them could probably be adjusted up (ie: thug maledicts).

>A thug forgoes all those other paths to pursue melee. Yes, they can learn some things in other paths, but not the higher level stuff and if they do try to climb another path, they are giving up thief staples like Gentle Walk, Knife, Cheap Shot, Shield Block, etc. to do it.

That is kind of a weird argument, and to sounds similar to someone saying that their Offense/Water shifter should have a flying form. There is a reason that there is a cost involved with the skills you listed, and its because most of them (other than shield block imo) are WAY more powerful tools to have than things other classes possess by default.