I can only recount my experience when I was there last November. The line for the front was about 15-20 minutes. The others were pretty much a walk-on or waiting for one train to leave type of thing.
I don't ever recall Kraken having a single riders line. It wasn't too busy the day we went and it was a Saturday. HTH!
I would say that the front is worth the wait at least once. If you want to ride the front, head to Kraken first thing. The front seat line is way short around 9 am. As for single rider lines, there are none. There is a trick for single riders though. After you get off, hang around the exit area and look for empty single seats. There's usually some around. When you see one, head towards it and sit down. The exit gates usually remain open until the train is nearly ready to go. I did this and was able to ride Kraken about 5 times in a row. I even got an empty single front seat!
If the ride isn't too busy, you can probably do it. I rode the Hulk twice doing the same thing. Just remember to make sure it's an empty space. Don't kick someone out of their seat because you want to ride again. They waited their turn too!
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