ET tactics succor is particularly useful when there's a ton of aoe and you don't really need the shield afterwards, or when you want to help your whm that is struggling with mp.
Some very nice examples on how ET succor is useful can be found in alexander savage clears videos by elysium and lucrezia.
Not very useful on adlo imo, but you can always use it to save one AF and slightly increase your dps /shrug