Fully agree. Not only have we never received just one character at E3 (close with Ridley, but I'll count in Daisy), but it's been a really long time since we heard of a character (by E3- it will have been 7 months). We are to receive them all by February (and honestly I think thats the end of projected time frame, meaning we could get them all sooner). Sure Nintendo usually back loads years with content (making BotW all the more of a treasure), but we cannot actually keep a strong pace the rest of DLC time line without two at E3.
And honestly, Banjo and Kazooie would be a great fit alongside Steve. If one company were to get two announced at once, it makes sense to be Microsoft at E3- Banjo and Kazooie appeal to a widely different audience than Steve, who is often different from Joker (and all three have quite different aesthetics as well).
Then, August/September and December for the final two character announcements.