This past Saturday, Warner Bros. screened the first Suicide Squad teaser in Hall H at San Diego Comic-Con, and in my opinion, it was jaw-droppingly awesome, even more so than the also-awesome Batman v. Superman: Dawn of Justice trailer that came minutes later. The crowd reaction seemed enthusiastically positive, and the footage has now been released online for the rest of the world to see, so it'll be interesting to see if the public feels differently about it than the Hall H attendees did.
But there could be an actual, defensible reason for a disconnect—if one comes to exist.
For one thing, you'd probably be right in assuming that a lot of the people in Hall H were DC Comics fans to begin with, and thus, people who were already primed to like movies about DC characters. Yes, Fox Studios also had presentations later that day for other eagerly anticipated comic book-based films like X-Men: Apocalypse and the new Deadpool film, but Fox's panel was basically sandwiched between Warner's DC movie panel first thing in the morning and Warner's DC television panel that took up the night. Warner Bros. took up a large chunk of Saturday in Hall H, so a large number of the people who camped out to get in were fans of DC characters to begin with. The studio was essentially feeding people with content they were already going to like. (Unless the videos were horrible, which they weren't.)
For another, it's worth noting that Dawn of Justice was an extended trailer, whereas Suicide Squad was just a teaser. Teasers and trailers are two forms of pre-release content with different purposes. In Suicide Squad's case, Warner's claimed that the Hall H footage was only intended for the people there and never meant for the rest of the world. They only released it to the public because someone inside Hall H recorded it against the studio's wishes and uploaded it to the Internet. Suicide Squad's teaser presents the movie's basic storyline—about a government agency either motivating or outright forcing supervillains to go on missions—but is vague on plot details or who the characters are. If it had been a full-fledged trailer, some of this would've been better-explained. But again, Warner's may not have felt the need to do so since they were screening it for DC fans who already know the Suicide Squad characters from the comics. If the general public is confused about the motivations or storylines, one could say Warner's didn't feel the need to explain it to them because the studio never meant for them to see it.
Dawn of Justice was in a similar circumstance not too long ago. Warner Bros. released a short teaser online that polarized the audience. People knew that Batman and Superman would fight, but they didn't know exactly why, nor did they know much else about the plot . That's because it was really just a teaser, not a full-length trailer that's supposed to clear up a lot of the mystery. Fast forward to last Saturday though, and now we see a three-minute trailer that more clearly spells out the conflict and shows more of Superman's and Batman's motivations while it introduces Wonder Woman's and Lex Luthor's characters as well.
If there's been any confusion as to what any of the DC teasers were supposed to show, it's been largely because they were teasers—footage that's just meant to "tease" the major plot. Trailers are usually more developed. The problem is that most people don't know what the difference is between a teaser and a trailer, nor do they care, which is why studios sometimes get screwed over in how viewers judge their pre-release content.
For Warner Bros. and DC Comics, last Saturday was an important day for them, and they definitely made a great effort to put on a good impression with fans. The companies just have to hope that the rest of the world understands what they meant to say.