Okay, seriously, this champion critique is just getting ridiculous. It's basically turning into "dear god every champion has something they're really good at! HOW TERRIBLE!" You complain about a strength on one champion, and then when another champion has that as a weakness you're just like "eh, doesn't matter that much".
Diana
Strengths: AOE damage, ability to jungle as an assassin, some tankiness
Weaknesses: NO escapability, reliant on sustained damage for full burst combo, wonkiest skillshot in the game
Jayce
Strengths: Utility, ranged mode on a bruiser
Weaknesses: No ult makes his team fights really weak
Darius
Strengths: Ridiculous damage, ridiculousness stickiness, execution move
Weaknesses: Arguably more kiteable than Udyr, everything in his kit is reliant on him hitting you for a while (passive stacks, W refresh, ult execution) meaning that if he doesn't get those hits in he's completely useless, tremendously weak against armor stacking, needs to build squishier than most tanky DPS to get his damage
Hecarim
Strengths: Mobility, good initiation
Weaknesses: Very little CC, no burst whatsoever without ult
Ahri
Strengths: Great burst, huge mobility, true damage
Weaknesses: All skillshots all the time, needs to blow her whole kit to burst people (moreso than most mages, and puts herself in a weaker position than most when she does it)
I really don't feel like doing any more, especially since you seem to be skipping champions now just to ignore the ones that go against your main point. Champions right now are very unique, have tons of differences. Really your only legitimate point is that champions in similar roles build similar items and honestly that's not the most important thing in the game. A Darius and a Hecarim that both have the same generic tanky DPS build will each be an entirely different experience.
I will agree there needs to be more item diversity, but Riot is looking at that right now. There have been a lot of posts about it. They're interested in creating more items for literally every single class. The big problem right now is that the season 2 championship is looming ahead, and it would be a hugely stupid move to make big changes like that right now because it would risk screwing up the biggest tournament of the year.
Basically my point is that if you're bored with League of Legends now, wait a few months until season 3. They made some pretty huge changes towards the beginning of season 2 that I think everyone has forgotten, and I'd expect similarly big stuff to be coming up soon.