This past week my Tuesday group finished our 1-10th level campaign of 13th Age. I've talked about this before, but for this campaign we rotated GMs every adventure (3-4 sessions) and allowed a roster of multiple characters per player, choosing PCs at the beginning of each adventure. Our goals for this campaign were threefold: 1) to give more of our group a feel for GMing 13th Age, 2) to play around with different combinations of characters (particularly the new stuff in 13 True Ways), and 3) to see how Epic Tier plays out.
For what it's worth, I've never liked Epic Tier in D&D. In 3rd and 4th Edition once a character got into the teens, which wasn't even Epic Tier yet, things got too complicated and/or balance suffered. On paper 13th Age seems like it might avoid the worst of this. Most notably, balance suffers a LOT less than in D&D, but it still wasn't perfect.
The 13th Age encounter building chart is a nifty thing, though it does have its quirks. It didn't take me long to realize that "fair fights" weren't particularly dangerous. Last year in my campaign that ran from 1st to 5th level I got into the habit of starting with double-strength encounters, but I'd go up to triple-strength and the PCs managed to win those. "Fair" fights would end up being handily dispatched before the Escalation Die even hit 3.
But a strange thing happened as we started gaining levels. The encounter building chart says that in Champion Tier a "fair" fight is an equal number of normal monsters of character level +1 (instead of character level). In epic, this becomes character level +2. Odd, to be sure, but certainly this accounts for the fact that while PC numbers and monster numbers keep pace, PCs get more toys with more synergy, which give them an edge. Except that's not quite how I've found things to work. A lot of higher level monsters ALSO get improved nastier abilities, and it's explicitly stated that the encounter-building math only takes into account raw numbers and NOT special abilities. It's what makes a 4th level dragon better than a 4th level hobgoblin.
Using the Champion tier guidelines as-is, I noticed things getting a lot tougher. My double-strength fights, which were baseline in adventurer tier, really put the party through the ringer. Encounters of 1.5 strength were more reasonable. Then came Epic. One of the first Epic encounters that I put the PCs up against was a pair of leveled-up Frost Giants from the Bestiary (all damage was scaled exactly using the monster's percent damage compared with the baseline stat chart). It was a "fair" fight exactly, and less than what I'd planned on having them face (they bypassed a lot of potential enemies and didn't raise any alarms). Within one round the wizard was dead. The (optimized, animal companion) ranger didn't last much longer. That's half the party down, and only the chaos mage's Unsummoning spell allowed the rest to actually win. I was pretty shocked, to say the least.
I talked this over with the group and we agreed that whoever was GMing would use the Adventurer-tier challenge levels from the chart. That is to say, a "fair" fight at 9th level would be a number of normal 9th level enemies equal to the PCs, instead of 11th level monsters. For the most part things worked pretty much as they had in Adventurer tier. The "fair" fights usually weren't too much of a problem, but double-strength encounters were pretty challenging. Anything over that was potentially campaign-loss-worthy.
In other words, the Epic tier math still works great from a balance standpoint; it's just the encounter building guidelines that are off. And I can live with that.
That said, I still don't like Epic tier. Number inflation is a huge problem for me (I've written about this from a GM's perspective before), with the disclaimer that most of my group doesn't have a problem with it. Everyone's turns simply take a lot longer to resolve, with the end result being fights that last about as long as they did in 4E. No, really, we've had 2 hour long fights in 13th Age, and a lot of the PCs are playing "simple" classes.
I'll use my own archer ranger as an example. Her baseline attack damage with double ranged attack is 10d6+18. I've simplified it further to 4d10+39 (ever since Champion tier I've been rolling 4 dice at even levels, 5 at odd levels). There's more than a trivial pause to add everything up, especially when damage starts to get added from improvisational stunts, crits, or other PC abilities, not to mention the fact that most of the time she gets a 2nd attack off. It simply takes longer than adding 2d6+4. I can do that almost instantaneously, and then add some narrative description to boot.
Worse is that almost everyone else in my group refuses to use dice conventions. They'd rather roll 10 (or more, for certain abilities and spells) dice and that takes even longer to add up. That might be a problem specific to my group, but it's still something that kills Epic for me.
In some ways I'd rather run a campaign from 1st to 5th level, awarding incremental advances every OTHER session and having it run the same amount of real time. But on the other hand, I really like a lot of the higher-level abilities that PCs get without being an unbalanced mess. Characters have enough options to feel like they can deal with almost anything, but the choice-paralysis and never-ending interrupts and minor actions of 4E are nowhere in sight. I suppose it's fair to say that I have a conflicted relationship with Epic level 13th Age.