How about keeping the Medium Armor and 17/14/14/8/12/8?
This gives at least decent DEX saves and better Stealth though your Stunning Strike DC would be terrible.
I am thinking about heavy armor and 17/8/15/9/14/8. The thing with medium armor and githyanki is that 14 DEX is still a 7 point investment into a stat. In my experience with stupid builds, adequately spraying into 4 attributes is impossible, thats why you need to limit the core to 3 or even 2 if possible. STR is a staple because of the racial mod. The only stats that can be 'cheated out' of the formula are CON and DEX - the first one can be substituted with Tough feat which equals 7 points in CON during the character creation (in terms of HP, STs will be sh** still) and the second one can be bypassed by heavily armored feat.
