You kind of missed the last two letters…
Anyways, Bleach is a good series, but I really wish that Kubo would get around to developing the characters that he created. Sure, this latest flashback developed the Vizards, Aizen's group, Urahara, and Yoruichi, but there's a bunch more characters out there that could still be developed (Isshin, Shunsui, Tousen, Gin, Yamamoto, and Komamura, for starters).
Wow, give the guy a chance. Kubo has shown us a little bit of development on Gin and even a little of Tousens. It's obvious he will get to them on their developments. Obviously none of those other heavy hitters you mentioned haven't even had a serious fight yet. Undoubtably he will give the audience a flashback on many of those characters.
Name one character that has been developed that doesn't matter. In the grand scheme of things, all of the characters that Oda develops seem to have a reason for being developed that has to do with progressing the story.
Then tell me what happened to all those secondary characters from all the islands Straw hats left?. Who cares right now about Nojiko, The flying fishriders, or Pell right now? (who was proven to be alive after the Alabasta Arc FROM A CITY DESTROYING BOMB BWAHWAHHAAHWAHA!!)
There are hundred of useless characters in One Piece. Hell…even inside the straw hat crew only Nami, Luffy, Zoro, Ussop, Sanji and Robin matters.... all the rest are treated like fodder or comic relief. And the characters are always the same: Luffy as an imbecile tard who wants to became Pirate King, Zoro just kills random swordmen until Mihawk and Sanji only got development in his intro arc and just try to look boss with his cigar.
This is coming from a guy with One Piece as #1 on his anime list.