This last bit is the reason why I'm asking these questions though. If there was truly "pretty much no way it was going to win" I'd consider that horribly broken. Granted it's a brute not a solo, and it's a level 27 monster, not a level 27 encounter but it's still a level 22 encounter (25 if the minions were included). I would expect it the other way around. A battle with any creature 1/3 of the way through the maximum possible levels should result in a TPK unless there are extraordinary circumstances.
To me this entire battle indicates a serious breakdown in the system at those levels. I'd like to see how this feat was accomplished because ultimately it factors in to my decision on whether or not to continue with 4E.
You're both forgetting the action economy.
I haven't played at Paragon (or Epic) tier yet, but already at Heroic tier it's apparent that 4E does not work in the same way as 3E does. (In my case, the eyeopener was when the level 1 party simply steamrolled a level 8 Lurker).
The average party of five characters will simply win against a single (non-solo) opponent, even one many many levels higher than that party.
It's simply not possible to take a single monster, look at its XP, and arrive at a representative encounter level. 4E simply demands more actions for a fight to become remotely even.
That is, more monsters (either more individuals or monsters Solofied, preferably according to recent - MM2 - guidelines, as MM1 Solos were given too few actions on average).
So in 3E terms, yes, 4E is "horribly broken".
However, in 4E terms, this fight is simply not one the game supports. Add one or two more Balors, and you'd quickly look at a TPK.
The reason is that everybody is incredibly resilient in 4E, with player characters having very strong replenishment options. Combine this with (compared to 3E) very low damage output (on the part of even Epic monsters), and you should quickly realize that any single monster will simply fall unless he can burn through the party's hit points faster than he can heal up.
And that simply does not happen unless the monsters have approximately the same number of actions (attacks) as the party (i.e. about 5).
Having only two (judging from the thread now, haven't looked up the Balor) simply does not cut it against the healing capabilities of a party even a whole tier lower on the awesomeness scale.
Like any other 4E monster, the Balor needs allies to present a challenge. On the other hand, even one level-appropriate ally should make a huge difference in a fight this skewed. (However, I wouldn't completely rule out victory for a well-prepared Paragon party even against 2 Balors. Monsters simply does not do scary high damage with any attack at all).
Incidentally, my proposed houserule (adding 1d6 per level of difference to any single monster as "striker-ish" bonus damage) would have worked wonderfully in this instance. Say the level difference was 11 - that would give the Balor an additional 11d6 each round to apply to those of his attacks that connect.
"wonderful" and "wonderful" - it would ensure a TPK, making the game look and feel more like 3E. Of course, it goes against everything 4E stands for. However, not everyone likes how the solution to every 4E problem is "more monsters".
For the purposes of this thread, however, I'm bringing it up as an example to the drastic measures needed to make 4E work the way a 3E DM would expect.
4E damage output simply is geared towards the party winning. Even against absurdly high-level foes. (Unless these are given Solo-like properties, or to be direct: unless they are given enough actions to match the heroes)
It's all about the economy, really.