I concur. I share DMing in this campaign (we rotate after each adventure but all our adventures are linked to the same evil plot). I wish more creatures were like this too as it was very fun (though very tough) but it does seem designed differently than all the others since there are no recharge powers and what not. I was just curious as to what others thought.
It is a neat monster, design-wise. What I find odd about it is that fluff-wise it is more of a random/filler encounter monster, something that you encounter on your way to somwhere rather than as a climactic fight, but it really has the potential to overshadow whatever you do for an end fight.
I ran a balhannoth reflavored as a squid creature whose tentacles were coming up from all over a lake the party was going across on tightrope... people falling down, jumping up, tossing enemies in, etc - it was grand fun.
I could see where it might be frustrating to fight, but I'm not sure it's unfair necessarily... it's definitely elite, though.
I used one as a "released by a big rockfall and now it's eating the dwarves" kind of thing.
It was awesome- it engendered a much more exciting fight than most monsters have. One of the best. But it was the only monster against a lower-level party (prolly around 10-11th at that point, I think).