Lethality should be treated like Crits
For both you should need a lot or they are mostly useless. Also nerf lethality numbers on items, and add a rune that triggers when you have X Lethality to give you plus +10. For example if X is 45, then once that is reached after buying 3 items, you get an automatic kicker of +10 to have it make more sense.
Learning League is hard, but fun (which is why league is 20x bigger than DoTA). I think giving people a second to think, would compliment gameplay. The issue now is pace of the game, and snowballing. Early power should come from singular effective spells and chaining them. Later game certain combos and risky dps should rule.
and
or you do no damage to most of the team. Now you can get 1-2 leathality items and then build from there. Which is different against every team comp.