Slotting slows - does it make a difference?

I have a level 42 dark miasma defender, and I slotted up my tar patch with slow enhancements, bringing the slow component from 90% slow to 177% slow. However, I'm not sure that actually does anything. It doesn't seem from my perspective to make a noticeable difference in how much it slows down enemies that it worked on before, and it still can't touch warwolves.

So, my question is, what exactly is the purpose of slotting slow enhancements, and is it worth it on tar patch?

Werewolves cannot be slowed. For tar patch I used to slot with just three recharges since my builds are usually tight. If you have an extra slot to spare and you want more slow out of TP it's not a horrible idea. Usually people can find better spots for them though.

90% is enough to slow most enemies the same level as you to the movement speed floor (10%). Additional slow strength lets you do the same against higher level enemies. Try unslotted versus slotted Tar Patch against +4s and you'll see the difference.

Whether it's worth it depends on a lot of things. Does your secondary have any slow or immobilize effects? Do you regularly fight above your level? Do you normally team with others that would make extra slow movement debuffing irrelevant?

For me, I usually find extra slow movement to be unhelpful (Caltrops being a major exception). I either have more than I know what to do with (I'm looking at you, storm summoning!) or I have other ways of controlling the battlefield.