Yeah I just find that so much of the modern meta, at least over here, just blows IJ up to quickly or ties you down in ridiculously long melee. Tzeentch, fyreslayers and OBR all just grind you out and one of the things you get out of Big Waaagh! is ridiculous MW output from bonesplitterz and far more reliable casting while being far less CP dependent. On the other hand big waaagh! has basically switched to huge blocks of infantry with a ton of wounds so as you said it's a very different playstyle.
Oh on the ethereal amulet point, since slaughter decided to drop realm artefacts I tried the -3 rend at heat 1, holy gods was it good. The only time it sucked was vs etheral amulet stonehorn but without it I cream it in a single round. Should be interesting to see how the different factions suffer not having the realm artefacts.