Thank you for replying! No, I haven't changed any models. My process was:
Install fresh Skyrim, run once, download and extract the main files from DynDOLOD resources, download and run fresh TexGen at default settings, fresh DynDOLOD with High settings clicked and Ultra trees checked, and xLODGen.
This has been driving me mad for sure. I must be messing something up, some setting I have wrong or something but I don't get it.