As for design examples: personally I am fond of soft enrages. Difficult phases:
e.g. very heal intense or heavy on tank cooldowns or generally progressively overwhelming via add spawns etc.
Imho the above is much more interesting than some binary "yo, lets see if you can dps the orb hard enough to not make it go boom and instagib the raid".
As for the hard enrage: you need those but here I also prefer a gradual overwhelming enrage (eg: boss collecting damage up stacks etc) to "ok playtime's over!11" hard instagib casts.
From a players perspective, I find it more fun if you can eek out a few more precious seconds by insane CD stacking or creative tanking compared to the alternative.