If you're not serious about your game enough to have Nexus 4/Galaxy Nexus, Nexus 5, and Nexus 7 and Nexus 10 on your desk simultaneously, then optimizing your game is not worth it. This is an incredibly painful process even when you develop natively, and there is no painless shortcut to it. The SDK emulator will let you know if there are stretches or gaps on certain resolution, but won't test your performance, especially on mid-end and lower devices.
But no matter what you do, there chances for undetected device-specific bugs are nearly guaranteed.
My story: 3 days post-launch, I was freaked out that my game was horribly broken on 1920 x 1280, just because a friend let me borrow his tablet. I also got a deal on 100%Indie, but unable to take advantage of it because of a Samsung-specific bug that was absent from the 7 devices I tested on.
You'd just have to deal with it.