On Tharridon - STEALTH and INVISIBILITY no longer work, FULL STOP.
It's irrelevant of your level, class, skill etc... Even when I walk around town as a level 8 warrior noob with no buffs, no groups, no equip - NOTHING, I can clearly see level 50 rogues stealthed and level 50 sorcerers invisible once they come in 'range'.
So yes, they completely broke both these abilities, at least on Tharridon.
In regards to bard Invis - the only reason it appears to work (again, on Tharridon) is because of a) The lose target on Invis bug combined with b) the delay in 'detecting' an invisible/stealthed entity. When the bards pulse invis every 6 seconds there isn't much time to actually see them, in between the two above factors.