Adelard is pretty decent with the option of either being a debuffer or healer with some nice damage skills, depending on what you need. The biggest difference being ~500 health, no limit burst and 18 less MAG with no fast cast passive when compared to the UR Miranda. However any Miranda players should max Adelard as his TMR is the best in slot for Miranda or any future Red Mage (Okay stats with +15% magic damage dealt).
His fast cast is a main skill so all his subjobs can use it... also if the RDM is playing support role, rather than damage, Dario TMR is better, some have been saying the AP bonus does apply to TP skills
He's only capable of middling damage, worthless for hard content, but he is fun to play as, and a good support, though outdone by ayaka...
jam thrust and fast cast are main skills, echo takes the latter further, has the standard whm buffs, with curaga, and the standard debuffs, with imperil... and for magic damage, which he's better off with, grm has ruin.
I'm using him for pvp, mainly because he can use revitalize and jamming thrust, and able to provide some decent healing.