Earthing Rod has only 1 problem: It is not blender-friendly on a V Lord.
Only the bearer of the rod can re-roll a miscast, and those points remove the 1+ AS or the OTS in a Lord.
Besides, one must be fully aware that Blender lords are there for close combat, and magic support... not heavy casting (well.. they CAN since they can be Lv 4 but... most of our lore is 2-diceable)
Indeed, if the Ogre Blade and the Talisman of Preservation cut it for you, then yeah, take the rod and be happy.
If not, use it on the model who IS going to cast a lot of stuff, like a Master necro / Lv 2 Shadows or Death Vampire / Necro (I mean, the model who is always goint to throw 3+ dice in every single magic phase, like with Spirit Leech / The Withering / Enfeebling Foe / Mindrazor, etc)