With the last few updates, quite often this becomes an issue ONLY IF the mod in question needs to overwrite any of the FE Legendary Heroes/Data/English files. Some things have to be changed directly in those files, so if they get overwritten, they can break a mod.
The modding community tries to stay out of this folder as much as we can, but some things just aren't possible outside of that folder, if you are modifying existing values (say, buffing a monster).
What I do, from a modding perspective, is to shut off autoupdate, and then if I read about a new patch here I copy the current /English folder, save it in a safe place, and then enable/do the update, and disable autoupdate immediately afterwords. That way I still have the old values on hand if I need them for some reason.
From a player perspective, if you were asked to put any files in the /English folder, you may need to get updated files for that particular mod, assuming the Modder in question is on top of things and has a new release to tie in with the new patch. A quick way to check is to have 'DateModified' enabled under folder options, and sort the files by date modified. If a modded file you added to /English before has the most recent date on it, there is a good chance that the mod values have been overwritten. If the modified date for said file hasn't changed from the date when you dropped the modded file into the /English folder, and substituted/replaced said file, you should be golden.
Also, if said /English file deleted any existing values (say, deleted all of the current Sovs), any other files that are dependent on said values may break. Usually, though, said value calls need to be changed in the other .xml files by the modders anyways, so you'll note the 'updated' file with date modified, but if for some reason the Stardock guys added something that was related to the deleted stuff, that could also break things. I'd say that this happens very rarely though... Again, the designers of well supported mods will probably be on top of any conflicts should they arise, so keep an eye on their mod threads for new posts when a patch comes out.
Hope this helps!
