I also searched and searched and thought this can't be possible?! I have hundreds of hosts and can afford to patch 2, 4 or even 10 at the same time. Otherwise it just takes too long! Quick Boot is cool, but way too few models are supported (for example, Dell R630 is supported, but M630 not, hmmm?!).
VMware, bring that option back!! It's ok if sequential is the default (or if hosts are not in maintenance mode already), and I understand it for vSAN enviroments, but otherwise, HELLO?!
