Seems to be a lot of dick swinging going around here in-between the useful information.
From my experience I used lumi staff 46-49 to non-stop quad the shellcatcher otters in Cobalt Scar that roam into the water. It was fantastic for leveling 46-49. Once I got to 49, I almost exclusively used the 49 Quad nuke because my druid was very well geared and Mana almost was never an issue, though I would use the lumi to finish off quads if I ever ran oom.
I leveled 49-54 in Cobalt Scar off wyverns/drakes, and due to the fact they are usually contested by at least 1 other most of the time, I saw no real use for the low dmg lumi staff did compared to their hp pools. I also I had to wait for respawns usually anyways, and I enjoyed some down time to do r/l stuff between quads.
That said for a lesser geared druid I'd see great use in using lumi staff to quad from 49-54 as well, as insurance for if mobs resists or hps force you to run oom before the kite ends. When root rotting it can be used to finish off mobs if you run oom as well.
All the above is from solo experience, from a group standpoint not sure the long cast does a lot for you, and there are probably better things you could be doing to benefit the group through CC/spot heals/nukes/stuns/harmony depending on indoor/outdoor.
TL
[You must be logged in to view images. Log in or Register.]R - for a lesser geared druid imo the Lumi staff has significant value from 46-54 solo, and minimal use at any level in a group. 55+ it becomes a nice to have for insurance of free damage if you ever run oom, though at that point you're quadding/rotting mobs that have too many hps for your Mana pool and I'd find a new camp or buy some cheap +Wis and +Mana gear to get it up a bit and try again. If you can afford it by 46 buy it, it'll be great 46-49 and good/insurance 49-54.