The error with this is that it assumes mechanics are the primary driver behind interesting boss fights. This is true to some extent - a straight tank-and-spank with nothing else happening would be very boring. But the key factor is that mechanics are only interesting if you can't ignore them.
- Marrowgar is easy now because, well, it doesn't matter if the whirlwind hits you or if you leave a dps in a spike for 15 seconds.
- Deathwhisper is boring because you can easily kill the add waves, dps the boss down and never hit enrage - and the Death N Decay and add damage isn't that impressive.
- Gunship has no real dps and barely any healing requirements - if you are undergeared you can just have your tank go over less often.
- Saurfang is the most difficult of the first four - it has an actual dps requirement, although not a very high one. With proper positioning we saw 3 marks in 25-man this week, and zero in 10-man.
To say it another way, what makes boss fights interesting is dps and healing requirements. Not by themselves, but because they force you to pay attention to the weird stuff bosses do. If Marrowgar has a tight enrage and his whirlwind will two-shot you, then suddenly it's an awesome fight. Did the mechanics change? No - but they became more important.
The same is true for practically every normal vs hard mode, and it's why I expect ICC Hard Modes to be awesome. Every fight so far looks like it could be a blast on heroic, and Blizzard hasn't disappointed in the past.