Isn't it a conditional subjunctive (of comparison) ..
I think you are 100% correct. I consulted my trusty A+G New Latin Grammar and found it under section 524 "Conditional Clauses of Comparison". The most relevant example they use is this:
quasi vero non specie visa iudicentur: as if in truth visible things were not judged by their appearance.
Good eye and thanks for the pointer.
...in a dependent clause.
main clause // apodosis = hi ignavissimi homines omnia ea sociis adimere/adimebant
subordinate or dependent clause// quasi iniuriam facere esset imperio uti
I am not sure I agree with you that it is a subordinate clause where the apodosis is supplied by "hi ignavissimi ...". My understanding is that in such constructions the apodosis is assumed.