After having thougth about it, I really get the feeling that SAM and RDM will be coming in 4.0, and both in the role of Support DPS. RDM just feels like it would fit as a support type class, and with WM/GB they could add a mage mode which you turn from stabbing to casting. They could offer something similar to BRD's Foe Req.

SAM however, while I fully understand the push for tank or solid DPS, would make an interesting Support DPS. Before we get into the romance of the samurai as a swordsman, remember that they are often seen as leaders/generals. Putting SAM in with the standard support abilities in the form of Kiai's, debuff's inlcuding the slashing debuff as sword techniques, and keeping them always mobile would completely shake them up from what most people would expect.

As it stands right now, I really do not want to see another tank or healer introduced in 4.0. I'd rather see them get those two roles solid over 3/4.0 before new ones, ideally BLU and DNC, come in to be the new guys.

But more on topic, while it was a good read OP, I'm still incredibly bias to BLU as a tank over RDM