Not inconsistent, just vague. Kubo was screwing with the audience again.
Vastorode are hollows that are as strong as shinigami captains. Adjuchas are hollows that are as strong as shinigami lieutenants. Gillian are hollows that are as strong as seated shinigami officers. Turning a shinigami or hollow into a hybrid multiplies its power by 2-5 times. All the arrancar (hybrids) we've seen fight so far, except possibly for Ulquiorra, have been based on adjuchas or gillian.
The fights in the arrancar arc were between strong gillain arrancar and strong lieutenants/weak captains. The fights in Heuco Mundo were between mid-level captains and high-level adjuchas arrancar. The fights in the Winter War (which for plot related reasons Aizen is guaranteed to win) are going to be between strong captains and vastorode arrancar.