Yes, I'd agree that if deer are the only food source in the area, especially winter months, the coyotes will take them down. In my experience, coyotes don't normally "pack up" this time of year unless big game is all that is available. In fact, this time of year is coming into breeding season real soon and most coyotes are extremely territorial right now. Not uncommon where I live to only see singles and occasional doubles this time of year. Now a couple months ago, seeing "packs" would be more of a normal thing, because they haven't always dispersed the pups by then. This dispersal is also somewhat dependant upon prey populations and coyote densities.
In some years past, I've personally seen as many as 15 coyotes in one group, but that is certainly not the usual.
4 coyotes would probably get a deer down, but they would no doubt sustain some injuries doing it. I've called in many a deer with coyote calls, both howlers and distress sounds, and they come in ****ed off; I mean ready to stomp some coyotes butt into the dirt, snorting and jumping up and down and pawing the dirt type of thing. I've even had coyotes coming to the call and deer would sometimes actually get get there first.....once the deer are on the scene, usually the coyote won't approach much closer. They are alot more brazen when their "packed up" though.
You have a valid point, in that the Eastern coyotes are bigger, and they probably do act differently than our western ones. Similar can be said of the wolves inhabiting the great lakes areas, they are simply not the same wolf that is killing all the elk and moose in the Rockies right now.