Evocate, evocate, evocate
The way that the talent tiers have been designed is usually somewhat thematic. So you have the CC tier, the movement tier, the bomb tier, the shield tier. Tier 6 can best be summed up as the "carrot and the stick" tier. That is, you get both. The carrot is that you'll be regenerating mana and gaining a necessary spellpower buff - the stick is that you need to do something onerous or frustrating to get that buff.
For at least fire and frost, Invocation is the default talent choice. There may be some situational use for Incanter's Ward but by and large these two specs will be using Invocation. This means you'll be evocating constantly. Possibly until your raid group makes fun of you, if you happen to be me. You'll be evocating at the mailbox, at the bank, during any idle moment. It becomes a compulsion. I don't even realize that I'm doing it any more.
So if you are using Invocation, odds are good that you're tired of evocating. Some improvements were made to Invocation early on in the expansion, and they were a nice quality of life thing - a longer duration on the invocation buff as well as removing the cooldown on evocation. Still, the talent required a fairly large adjustment in terms of gameplay. You need to learn when you'll have a safe moment to evocate. With the cooldown removed at least the penalty is lessened -- if you accidentally have your channel canceled, you won't get the buff, and before this was changed it meant that you had to wait for evocation to come off cooldown before you could channel it again. All of this is time spent not DPSing.
I disliked Invocation so much that I tried to use Incanter's Ward instead. This comes with its own set of issues, specifically -- timing the shield to maximize the absorption effect and thus the damage buff gained thereafter. After too many shields that I popped too early (or too late, just after expected raid-wide damage) I gave up on this talent. Back in the day, Incanter's Absorption was a situationally useful talent in the arcane tree, but our DPS didn't hinge on it.
Finally, what about Rune of Power? Rune of Power is the mandatory talent for arcane mages. They rely so heavily upon constant mana regeneration because of their mastery and so it is generally the only viable option for them. The stick that comes with Rune of Power is even more punishing than Invocation, because it restricts your movement to within a set area. Sure, you can move your Runes when you refresh them (and you'll have to, because they only last a minute) but again that's time spent not DPSing. Time spent not DPSing is not fun.
Rune of Power got a quality of life improvement in patch 5.4 as well, increasing its range to eight yards instead of three. I appreciate that some changes have been made to make the talents less obtrusive. And that's really what it boils down to: talents should feel like a reward. These ones feel mandatory and needlessly punishing. They simply aren't fun. They don't make you happy to have hit level 90, and that's a problem.
Our talents vs other casters
I don't want to sound like I'm just fruitlessly complaining, here. I am confident that the devs will come up with some alternatives to the talents in the patch prior to the next expansion. They've already acknowledged that the talents need to be looked at. Until then, unfortunately, we have to deal with them. But what could mage tier 6 talents look like in the future?
I spoke to some of my caster friends and did a bit of reading up on talents that other classes have. Elemental shaman have this one, Elemental Blast - it's a damaging spell followed by a random stat buff on a 12 second cooldown. I'd be happy enough with a spell like this (mage flavored, of course) that caused damage and then granted a buff.
Balance druids, in keeping with the hybrid nature of their class, get Heart of the Wild that increases their Stamina, Agility and Intellect by 6%. It's also a cooldown that allows them to perform outside their given role for 45 seconds on a six-minute cooldown. Obviously this isn't appropriate for mages, but I'd be happy with a flat stat buff in combination with something else, too.
Finally, as the other "pure" DPS caster class, unfortunately I have to talk about warlocks. It pains me deeply to admit that their talents are better than ours. I had to talk to a warlock to get this information, too, then I had to wash my robes repeatedly to get that fel stink out of them. I suffer so that you don't have to, mage friends.
The two talents warlocks are most likely to use are Kil'jaeden's Cunning, which allows them to cast a nuke (depending on specialization) while moving. I'm not too jealous of them having this one, since we have movement stuff covered in other tiers with Ice Floes and baseline Scorch for fire mages. But they also have Archimonde's Darkness, which grants two charges of Dark Soul. The benefits of Dark Soul vary depending on specialization, but they range from a spell haste buff to a crit increase. So that's a straight up cooldown/buff for them, but not one that requires constant maintenance.
New hope for tier 6 talents
A new spell, or a buff (with no drawback) or something that augments or amplifies an existing spell would be suitable for our Tier 6 talents. I'm not looking for something unbalanced here, we have to keep it fair. I like the mage/time manipulation association, why not a talent that lets you cast Alter Time an extra time? Or something altogether new in each of the three flavors. An icy boulder that actually does appreciable damage! Or a wall of fire like mages get in Diablo. How about a three-minute cooldown blast of arcane energy to make a warlock's eyes bug out?
Basically, my wish list is talents that fit these criteria:
1) Something new or unavailable without the talent
2) Balanced and on par with other classes
3) No drawback to casting it
The damage gained from the 90 talents could easily be rolled into our spells themselves and the talents replaced with something exciting and new. What would you like to see our 90 talents adjusted to? I'm sure you're just bursting with ideas. Share them in the comments. I'm not a game designer, but I trust the devs to adapt as necessary and come up with tier 6 talents for us that are truly great. We may have awhile to wait before that happens, but we can dream.