what else can you tell me about why batch sparging pulls more tannin?
I either misspoke or you misread.
Batch sparging is LESS likely to pull tannins. Tannins are extracted at elevated pH (as in the mash pH is greater than 7), which is not going to happen with batch sparging, esp. with our water.
I would say you don't need a plate for batch sparging. I have batch sparged many beers. Here is my process:
Heat up strike water
Add it to your mashtun (mine is a cooler)
Add your grains, mix thoroughly, make sure temp is right, rest for ~60 min.
Collect first runnings in brew pot.
Batch sparge, mix thoroughly again, wait a min. or two
Collect second runnings.
Boil that mofo.
*Note: your infusion (60 min rest) water amount and batch sparge water amount should be roughly the same. I always batch sparge with 3.5 gal of water. And I use a ~1.25qt/lb for the 60 min rest (the mash). Then I topoff with ~1.25 gal for a mock mash out (temp never gets high enough). Then I vorlauf and collect first runnings......
Again, where did you get the idea of your off-flavor is from tannins? Are you just guessing? Did someone else tell you? Does it just not taste as good as you want it to? I know it happened when you switched to all grain, but there a lot of variables in all grain that could be off.