After a bit more tooling around with the skill tree, I managed to come up with another couple of variations on the Shield-Duelist based on Fencer's changes to my original, basically coming down to a split on the following:
A: 147% increased armor, 104% increased max energy shield, 50% elemental resist.
Shield Duelist A
B: 189% increased armor, 44% increased max energy shield, 40% elemental resist
Shield Duelist B
Any further tweaks/alterations would be interesting to see. At the moment I'm leaning way towards A, though I'm having to assume I'd be forced into B, as the extremely low intelligence will probably hinder the Energy Shield stacking as there won't be as much access to +ES gear as would be preferable.
Addendum: Came up with the following variation to make use of far more ES gear, with the points accessed, should only require 1~2 pieces of gear with +Int to use anything at all. It can probably be tweaked a lot more though.
Shield Duelist +Intellect