Superships are uncommon at times, but a recent engagement mission has increased their numbers. They are more powerful than Tier 10, but they do not make Tier 10 irrelevant by any means.
The Tier 5 - 8 game is really quite solid. You don't need to worry about pushing all the way to Tier 10 to have fun.
My best suggestion is to just play a ship you enjoy a lot. If you have fun, get the next one. If you have fun, get the next one. Over time, you'll either reach Tier 10 or find a different line that grabs your fancy, which is perfectly ok~