There's been something about masteries whihc have bugged me a bit and it's not very well explained anywhere I've seen.

On the offensive mastery tree there is sorcery which "reduces cooldown of champion abilities" by 3%.

Then on the Utility tree there is Intelligence which "reduces champion cooldowns" by 6%.

Following that is Presence of the Master which "reduces the recharge time of summoner spells" by 15%.

Maybe I'm being nitpicky with the wording, but my understanding is that these are different things. I'm not sure, but I'd like some clarification. My understanding is that sorcery only applies to to your champion abilities (qwer) and Intelligence applies to everything (qwerdf) and PotM applies only to the df skills. Am I off base here?

Also I know CDR from items and what not is additive not multiplicative, what about CDR from runes or from these sources?

Sorcery and Intelligence both only apply to champion abilities. Presence of the Master is only for summoner spells.

CDR from all sources (items, runes, and masteries) is additive, but tops off at 40%, so there's no point to stack it beyond that. You can get about 15% from just runes and the above mentioned masteries, so you only need to get 25% from items and/or elixirs/blue buff.

Ah, in that case PotM isn't really as game breaking as I originally thought. Frankly on a mage I'd rather do a 10-0-20 thing and get burning embers/flash or ghost or clairvoyance. Don't get me wrong it's useful as hell, but I rarely think oh **** if only flash was here 20 seconds ago I'd be fine. 85% of a crapload of time is still a crapload of time.

The way I like to think of it, the longer the cooldown of a summoner spell is, the more effective PotM is, since it's a scaling reduction rather than flat reduction. It also works on both of your summoners, and you can pick up the Flash mastery on the way down and get it to a reasonable CD when you take both.

That said, masteries are largely up to preference. I just don't really like Burning Embers because I typically save Ignite for after I've already blown all my cooldowns and just want to make sure I do enough damage for a kill without them being able to drink a potion. The extra 10 AP when it's on cooldown 1) isn't very much bonus damage on most skills, and 2) tends not to come into play when I most often use Ignite. I'd rather have it on a shorter cooldown so I could use it more often like this than get some free (but practically unnoticeable) AP.

Good points. I tend to use ignite rather aggressively especially if I know my opponent has a heal. That said, the 10 AP bonus isn't going to scale as well as being able to ignite 15% faster.

You are right that longer cd makes the skills scale better, but in the end the bottom of the two other trees (+4% more damage, -5% damage taken) seem more impressive. The thing is that the Utility tree has a much nicer buildup throughout as 6% CDR, +30% duration neutral buffs, +3% MS are far better than the buildups in the other two trees.

Ok last question, does the 15% from PotM scale before or after flat reductions to the skills (I.E. the revive bonus -30 seconds)?

I believe PotM scales after flat reductions from the other masteries. I haven't actually crunched the numbers, but that's typically how these sort of mechanics interact in this game (look at armor/magic penetration, for instance).

I agree that Havoc and Tenacity are quite powerful masteries, but they are made much weaker by the things you have to take to get that far into their respective trees - especially on mages. I honestly don't go 21 points down the Offense tree on anyone at all, although I know a lot of people like to do that on junglers. I just don't really see the point of most of the higher tier masteries in that tree. The Defense tree is quite a bit more attractive, but again, Utility tree just has so many options that can be good on almost all characters.

Alright thanks a lot, I'll be adjusting my masteries accordingly.