I don't trust Riot with large scale changes. The jungle changes are half and half (no more magus, more jungle camp executions this season than the previous two seasons combined, devourer too powerful in two different forms this season), and the AP itemization was an exception to the rule.
The most obvious example of Riot handling large scale changes badly is the juggernaut changes, which made four champions broken for several patches and is still giving the balance team issues even now. They pretty much destroyed the identity of one of League's most "hue-tastic" champions.
Before that, we had the support changes in preseason 4, designed to make supports have a "power fantasy" and "bring diversity to the role". That little trick brought us utility scaling and killed off the majority of sustain and poke supports for two seasons now. Colossal failure that still hasn't been fixed; and support is still an unpopular role.
And don't get me started on the tank changes that actually went really well inspiring diversity and bringing tanks back into the spotlight the vast part of the season, then got toned back just in time for worlds because worlds demands flashy plays that tanks generally can't deliver. They had a good thing here, but screwed it up because the number of people buying tickets to worlds is a higher priority than overall game balance and health.