The Longsword/HBS/Bastard Sword were in good places before and were very effective weapons. The reason for the change as I understand it is that they were underused on EU servers. On NA Longsword was already the most prevalent 2-handed sword on the battlefield (as per the last percentage stats I saw which are, admittedly, somewhat dated), so for this side of the pond the buff is likely to have the opposite effect as on EU (decreasing diversity instead of increasing it).
Danish (and german I believe) was still higher. Second, EU>NA. Seriously though, it's easy to argue that the danish/german(or just about any greatsword for that matter) were better than the longsword/HBS, through analysis and not usage statistics. Still, we need polestagger reimbursement and 1h cut weapons need a larger damage buff.
Even if people use the danish a lot less, a lot of people like the new German Greatsword and a lot more Dadaos and Miaodaos are showing up, same with normal Bastard Swords. The Heavy Great Sword now has a home albeit not a popular one, the change can't possibly have hurt the usage stats. I really don't see it making diversity worse. Worse case scenario, weapon names change but statistics stay the same.
Final note: Discounting gold cost, greatswords will always be more effective in strat than the shorter reach weapons.