Did you mess with the rmv2 file at all or only with the textures? If you're only messing with the textures, then you either exported wrong, or at the wrong resolution. The exported .dds should be in DXT10 format, which the Gimp plugin does not support currently, unfortunately, but Photoshop does. In most cases though, exporting as DXT5 will also work.
The default resolutions are:
wef_spellsingers_cape_01_diffuse 512x512
wef_spellsingers_head_01_diffuse 1024x1024
wef_spellsingers_legs_01_diffuse 512x512
wef_spellsingers_torso_01_diffuse 512x512
Make sure you're resizing layers before exporting, or the final image will be larger if any of the layers is bigger than the final image
If you DID change the rmv2 file, then you only changed the filepath on the low poly models. When changing filepaths in the rmv2 with hexedits, you need to change ALL the filepaths (ctrl+f -> diffuse to find each section easily).
Last but not least: if you messed with the .variantmeshdefinition file, then you didn't do it correctly: Spellsingers as you noticed use .wsmodels. It's not very different from adding the rmv2 directly, but you need to change both the VARIANT_MESH model= and the imposter_model= lines. The difference is, since it's a wsmodel, you will add the wsmodel file, instead of the rmv2 file. So the final line would be:
Code:
<VARIANT_MESH model="VariantMeshes\wh_variantmodels\hu1b\wef\wef_spellsingers\torso\wef_spellsingers_torso_01.wsmodel" imposter_model="VariantMeshes\wh_variantmodels\hu1b\wef\wef_spellsingers\torso\wef_spellsingers_torso_01.wsmodel" >
<META_DATA>audio_entity_type:wh_dlc_wef_elf_female_LH</META_DATA> <META_DATA>audio_armour_type:leather</META_DATA></VARIANT_MESH>
for example