Imo freekills (e.g. Range 2 destroy) is broken in general, since it defeats the idea of a minion structure.
Necromancer also gives the discounted Skelleton+++ as a bonus.

In Ryans guide Necromancer0 has an excellent rating along with stall pieces like Dryad and other free kill pieces like Ranger (In common and rare only Dryad0/+, Ranger+ and Millitia0 are rated excellent too in the guide, iirc, but some legendaries like pride would pretty sure be on a simmilar powerlevel and VM++/+++ ofc OP).

But notice, if you ban all free kill pieces, then Lich+ and base, while being much weaker than Lich+++, will get pretty uncounterable, so they would need a ban too.