Well the thing with this is that he is supposed to portrayed as sick and demented(and you will see that that is important soon

)
Also, it does take a little while, but the Nel/Nnoitra fight gets interesting so I can see why they didn't keep going with it(and lots of shows do that. they build up suspense and then go back to another story going on at the same time)
This episode was pretty good about keeping everything in the present tense and not going back to the past as much.
The next one will be Neliel's past and you will see what Donchaka(no one can spell it...) and Pesche were talking about when they said they haven't done anything yet...they AREN'T useless...as it may seem(duh! Useless characters never happen!). Not gonna say how or what though...
