A lot of people seemed disappointed but it is most likely because we already knew about a large part of the campaign so nothing new was really shown besides Warzone (which didn’t have any gameplay) :(.
I think watching some gameplay of Warzone and possibly newer 4v4 will be awesome.
They’ll probably most likely show warzone gameplay eventually. We still have a lot of E3 left. 
I thought about this too. The main reason people were not really impressed was because they dumped info too soon. That issue should’ve come after E3.
There’s some gameplay of it.
Warzone is playable at E3’15, expect lots of videos to surface.
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> There’s some gameplay of it.
It was a gameplay trailer. Just not a very long one.
I wish they would’ve given us some Blue Team gameplay. This reveal isn’t very exciting because it lacks context. I’ll compare it to the Halo 4 E3 2012 reveal. Going into that presentation, we already knew a number of things about the story: Master Chief would eventually be pulled into Requiem, where he would encounter the Forerunner Promethean enemies. The Didact was already basically revealed as the game’s villain to those with keen eyes at this point, so the Promethean presence on the Forerunner Shield World made a ton of sense. We also knew John’s mission: to link up with UNSC Infinity, which would also eventually encounter Requiem, and get Cortana home. With all of this premise in mind, it was really exciting to see UNSC Infinity break through that cloud cover and coast over John and Cortana, who immediately set a waypoint for a rescue. It was exciting to see the Prometheans in action, because we already knew their presence made sense on Requiem and we hadn’t seen them in-game yet. And, of course, the Didact voice reveal at the end was thrilling, practically confirming his suspected presence.
This reveal was fairly short on context, in comparison. They tried to cram it into the introductory video, but, even to someone super familiar with the lore (like myself), it still felt like a mishmash of place name callouts and nonsense. Why has Spartan Locke gone to the Arbiter and why is the Arbiter helping him? Besides that, we have no idea why John and Blue Team have gone “on board” this Guardian or why the Arbiter would know that. We don’t know why these Guardians have appeared. We’re not familiar with Sunaion. We don’t know why there are Prometheans on Sunaion. We don’t know why the Covenant is “crumbling”. We know next to nothing about Spartan Locke’s squad and we know very little about the character’s personal motivations in hunting the Master Chief (it sounds like he doesn’t really have any). Finally, the protector of the Domain - what? That was a huge reveal, but it doesn’t make any sense given the little information that we already know.
The gameplay did look exciting and cool and was a nice showcase of the game’s new mechanics. But, especially for lore fans, it’s hard to stand on that alone. The game’s premise is still absolutely hazy - we have no idea why the Master Chief has been called to the Domain or what he is after. This reveal was, in short, a whole barrel load of things that don’t make much sense at all, and won’t until we know more things.