And Akavir isnt ruled over by a Dragon, One of 4 major races is ruled by like you said a Tiger-Dragon. and all the Dragons in Akavir are Dead so how would they impart a force to invade Skyrim?
^^ That is true, however, Tosh-Raka and his ilk are pretty much the dominant race there. After all, out of all the races there, it is only Tosh-Raka that apparently can claim the power and ability to invade Tamriel. So for the sake of simplicity, it is easier to say that Tosh-Raka is essentially the Emperor of Akavir, even though officially he doesn't carry that title, and would probably spark a war if he ever tried to claim that title and enforce it on the other races.
And I never said that that there were any living dragons (other than Tosh anyway) on Akavir, only that Akavir is largely connected to dragons, its name meaning, IIRC, land of the Dragons or something similar to that. You also have to remember that Tosh-Raka transformed into a dragon, and we could guess that he could pass this trait on to his most trusted people or warriors or indeed the whole of his people. Either way, he isn't invading as we already know that the dragons of Skyrim are following Alduin, not Tosh. Besides, it can be assumed that more Tosh-Raka like dragons would look similar to tigers and what not, and the dragon(s) we saw in GI look nothing like the sort.