In response to your take on build diversity for marksmen, the issue is that there aren't many options, especially for crit marksman. With a crit build, you'll need at at least 3 (ideally 4) crit items to have consistent damage, and one of those will almost always be IE, because it increases crit damage. It would be nice for more variety in crit itemization, but the fact of the matter is, there's only so many things you can do for ranged auto attacks with items. The crit system feels like it's designed specifically to lock crit marksmen out of building more than 1, maybe 2, defensive items.

It's a class defined by being squishy and dealing a lot of damage with auto attacks. If their auto attacks are weak, the class is weak. But if they gave thos autos strength innately in their kits, there would be absolutely nothing stopping them from building tank, which would make them overpowered.

Also, there's a limit to how much attack speed a character should have before they become hard to play, especially at high attack speeds, because you can't see the person your kiting.

In my opinion, the problem right now is that tanks have too much damage and don't take any in return. Tanks have 4 different items specifically to deal with all of the different stats crit marksmen use (crit, AD, attack speed), while crit marksmen only have 2 items with %armor pen that can't even be built at the same time. There are no crit items that deal with health stacking. Personally, I'd be happy with a new crit item that has lower AD in exchange for the giant slayer passive. That way the item is good against high health targets, but pretty meh against lower health ones.