I agree with you on all the stat stuff Varang. Just with regard to Gith though, That at least can be explained by the fact that it makes sense the queen would send Gith that speak common to try and find the artefact. They probably could have done more to give them an alien, unique accent but creating a new accent is difficult to do and keep consistent, and can too easily end up silly rather than cool, so I can't quite blame them for not going that route.
Agree, but if you want to include an alien race as an integral part of the story, giving them their own language and accent is much more important than voiced squirrels or oxen.
They would send Gith who know Common, but not all of them would. There's a significant difference between two similar scenarios:
1 - They all speak fluent native English, or Common.
2 - The dragon rider speaks Common to you with a thick alien accent, but orders Sarth Baretha to kill you in Gith tongue. She responds in Gith.