[GAMEPLAY]Smite's new stack system is bugged; the CDR from Summoner's Insight does not apply.
With the Smite Stack System intruduced in patch 5.1, the mastery Summoner's Insight (10% CDR for Summoner Spells) does not reduce the recharge time for Smite.
What it does instead is reduce the 15 second cooldown timer between expending two charges by 1.5s, but that does pretty much nothing (as of Patch 5.2, it doesn't affect Smite at all), and comparing with other skills it is quite easy to see that this is not intended.
Every other spell works exactly the opposite way; see Corki's R, Velkoz' W, Vi's E, Zyra's W, Heimerdinger's Q, Azir's W and Akil's R for reference: normally, the recharge time is the one that is affected. I assume this was simply an oversight, considering that summoner spell CDR is only found in this one specific mastery and nowhere else.
I really hope this gets fixed soon, because the way it is now, not only is it inconsistent with everything else, the points in Summoner's Insight also seem to be just wasted. (And it quite frankly puts a needless damper on strategic diversity)