Why encounters with a difficulty slope are bad

[Deculture]

Good Design:

T1, T4
Garuda Ex, Shiva Ex, Levi Ex, Mog Ex, Odin
T7, T8

Bad Design:

T2, T6,
Ifrit Ex
Pretty much every fight in FcoB

Horrible Design:

T5, T9

I personally think they wasted some of the best mechanics in the Crystal Tower raids and put whats left over into coil.

I just wish there were more encounters with things to do beside having to focus on your main party role. Healers heal and nothing else, DPS do DPS and nothing else and tanks are useless 50% of the time because most fights don't even need 2 beside the odd provoke in between to share some damage.