Jumping in where angels fear to tread, I'm not sure about this so-called 'BBC Dip.' Up until the early 80's, I seem to recall BBC monitors were pretty flat all through and they'd written papers on how important dispersion off axis was (I think various BBC research papers can be downloaded if you google for them). The famous Spendor BC1 which the BBC bought in hundreds as general sound boxes, from which the little sold original LS3/6 was derived, was pretty well flat across the lower kHz region (the low bass was it's issue but not too bad if placed high up). It wasn't until the 'polypropylene era' that the upper mid dip was introduced on 5/8's and 5/9's and this may well have been for the listening comfort of near-field balance engineers for all I know, the more distant perspectives being preferred perhaps?
Dips at crossover are commonplace it appears but whether this brings iffy dispersion into it as here, I don't know. I thought these Focals may be better than this and at least the tweeter doesn't take your fillings out as the better passive models from a few years back could. I heard the £1200 Chora's not too long ago and liked them (apart from the 'leaning back' stance, but whether they too have the 'safe' lower kHz dip or not I've no idea..