Agreed. I'm not sure WotC knew how popular the Encounter Builder would become when Jonathan Tweet spearheaded (wrote?) the project for his home game.
I think the encounter builder is the 'low hanging fruit' in the DDI. I'm only guessing, but I think getting the EB to include stat blocks would deliver a lot of bang for the developer's buck/time. It is a tool that every DM could use, whereas the Visualizer, dungeon mapper, and VTT are highly dependent on your current gaming situation. If you have a face-to-face game, the VTT isn't of interest. If you don't care what your PC looks like, and you've been playing the game for 30 years with stick people drawings, the Visualizer is eye-candy only. The Dungeon builder would be handy for drawing out maps, and could save the DM a lot of time if it was powerful and easy to use.
My vote for WotC's next DDI tool would be the Encounter Builder.
Second place vote goes to the Monster Builder. Get it to
a) level up/down existing monsters from the Compendium
b) add templates
c) create elite or solo versions of monsters from the Compendium
d) save/open 'monster files' that could be traded and compiled by the community.
I'm not a programmer, but I'm guess these projects would take less time then the other main DDI programs. I have no idea how far along those projects where before they got put on the back burner, so they may take less time then 'pimping' the bonus tools.
Verys