I don't think Dragonite should be moved to B-tier. If anything, Genesect may have tamed its dominance since BW1, though I think 'Nite is definitely still a threat to watch out for. It can still utilise its bulk which gives it a niche over other dragons like Salamence/Haxorus, and is still capable of tearing teams apart when played well. Remember that Genesect is easily worn with hazards, so Dragonite can sweep when Genesect has been sufficiently weakened. Most players tend to also play pretty recklessly with Genesect, so putting a Fire move and/or Thunder Wave on something that lures it in is a very effective way of checking it.
On a side note: I think this list would be more useful to new players if there was a short sentence or two justifying the Pokemon's position in a particular sub-tier.