To the origional question. They all take 8 seconds from start of cast to release of rooting for lb3.
Tanks have 5s till rooted, healer have 2s (which means they are rooted the longest), melee/ranged have 3s, casters 3-4s till rooted dependent on ping.
Cast/rooted time is independent of the job specific animation length.
Instant in this game refers to the cast time required, not the time it takes to go in effect.
Wether you think rooting, effect delay, and/or resource dumping on death is "antiquated" or not is personal opinion. Personally I think its a good thing given how scripted this game is, these tools were clearly designed to be used at deliberate points of content, not as "oh ****" buttons.