There's two things that we can provide feedback on.
One is design changes that don't require fine grained details; like "actions can no longer be queued" or some other major change that visibly and greatly affects the dynamic of a class.
The other is balance changes that do require numbers and greater detail. This is something that we COULD damn well provide feedback on, if the devs started including that detail both in-game (how damage is calculated) and out side of the game in planned changes to damage/healing/whatever (i.e. 'CON spells cost 10% less mana' versus 'CON spells MP cost has been reduced').
Not only that, but having your players test a patch after it has gone live is the absolute worst way to develop any MMO and it's a precedent that died back in 2004 when WOW came out. This is why PTR's have been created and why patch notes for any serious MMO are constantly discussed and revealed as early as possible.
