I agree that tier 2 is the sweet spot, but I wouldn’t want to start in the sweet spot, or any growth at all takes you further from the sweet spot. If you start at level 4, the game just gets slightly worse every time you level up. If you start at level 1, the most fun part of the campaign is still ahead of you. You get to build up to it, spend a little time there, and then grow past it to the point where you feel ready to retire the character and start a new campaign. Better engagement curve that way. Plus, levels 1-3 are really the only time where combat feels scary, which I think is a valuable feeling to be able to grow out of by leveling up.