If Armstrong shares the space with Drac, then the barrier would be forced against Ringo, who is adjacent to Drac. Additionally, though, Greybar needs to roll spell resistance for Ringo, depending on where Armstrong ends up. Best case for Armstrong is that he ends up in the nearest square 90n65e and does not share the space. Ringo will then take a 5ft step to 75n55e (10ft away) and try a full attack. If Armstrong fails SR, the full attack succeeds (pending rolls). If Armstrong succeeds on SR, then the attack fails and Ringo is done.
I forgot how you guys rule, but for grappling I rule that they share space. I do this for two reasons: (1) it is consistent with mounts, and (2) it is consistent with ranged attacks (imagine a second archon also in the grapple but effectively in another space).