So far, you have tried to isolate skirmishes from most of the end-game rewards. I read comments that you wanted instance rewards to stay instance rewards, and for skirmishes to compliment, not replace these systems. (can't remember where, any link appreciated)
Currently, for the most part, skirmish rewards are cosmetic, or LI enablers (scrolls, runes, settings etc).
Now someone may be able to convince me otherwise, but I see no reason to limit rewards here in any way. Why are skirmish marks not exchangeable for all in game tokens or rewards? As long as you make the skirmish avenue a time and group size equal one. You don't want to see the current situation where 1 Moria instance and one DG instance are the only two you see groups for.
eg. a piece of +15 rad armour takes 1 hour of easy mode SH. Equate that with an hour of skirmish marks, add in a couple of 3 man only obtained skirmish marks, and your done!
Now, let me be clear. I'm not asking for the DN, watcher or BG type gear to be available here, just everything else (yes including the symbol).
As a second point, it wouldn't hurt the itemisation cause to put in a whole bunch of comparable jewellery and pocket items for skirmish barter. There's really not a lot around at the moment.
I'd still like to log in someday and see a whole bunch of glff adds for group skirmishes. At the moment, we are no where near that day.