Recommended level for Journey To Meridian

The enemies level with you up until Level 80 (I believe that's the number), so it really doesn't matter since the enemies in the battle will be scaled to your level.

Yeah I hit 60 once although in that playthrough I did do a lot of sidequests. Not because I had to but because I wanted too in that instance really. I would say that as long as you'er at least 45 you shouldn't have a problem with the end of the game because you'er powers that you've invested in should be at full strength by then (assuming you've been upgrading your powers right that is.)

I Went through the Game wound up with all Level 10 gear, weapons, armor.

I would recommend to have leveled up at least the three favorite powers you want to use in combination to be able to get the best combos and have the most fun.

That means that you need at least 63 skill points, which you have from level 15 on if I counted right.