Ditherering to me has a definite connotation of indecisiveness and/or time wasting - I think of it at physical more than verbal
I potter rather than putter.
I might also do a bit of faffing about (I'd see faffing as having a flavour of wasting time /aimlessness, whereas pottering would be unhurried but not necessarily aimless)
Blithering I have only come across as a emphasis to idiot "The man's a blithering idiot" - blather is, as amandaelizabeth says, rambling on - foolishly or repetitively.
Piddle to me is what puppies and very small children do (although more robustly (if I can use it without upsetting the filters) 'pissing about' means wasting time, messing around - If I heard someone talk about someone 'piddling about' I'd think they were using it as a euphemism for 'pissing about'.
I drive over the river Piddle fairly regularly.