No. Disadvantages that are balanced by advantages yield a net zero sum. It is not a nerf.
You seem to be struggling with the concept of "balance" here.
You claim that only 2 or 3 bows or worth using, and yet STILL need to ask me what the purpose would be? 
Yes, actually I seem to struggle how these changes can be called balance. I struggle to understand how its not a nerf for me when my arrows fly even slower now. I hope you dont assume nerfing every usable bow to get them in line with those completely useless right now is a valid form of "balance".
This is like lowering the speed rating of every 2h weapon except the german and danish GS by 70, afterward complain that they are OP and everyone uses only those two 2h weapons and suggesting to nerf them to get them in line to be equally useless so people start using other 2h weapons than german and danish, which sadly seems to be the standard crpg nerf policy.
Maybe I didnt choose my words carfully enough so I will adress this once more:
You suggest this expecting the changes will lead to a lower popularity of the famous bows and spread diversity. The goal as I understand is to see more tartar bows, maybe more nomad bows, maybe even more longbows on the battlefield. As of now almost nobody uses short, normal, nomad and tartar bow (except HA). Although you want diversity, meaning you want exactly these bows to get more popular, the very thing you suggest is to nerf these bows ? Yes of course, the zero sum thing. Lobbing and arrow over cover with my xray vision once a year or the fact that bigger bows get buffed is sure enough reason to take a useless small bow, that is even slower and weaker now, only because you know that that longbow from that guy on the other side of the map got a speed buff.
I can absolutely see no buff for small bows here. And without such a buff nobody will consider to seriously use them. What I CAN see though is a nerf for small bows. Maybe you thought that im kidding when I asked what the purpose of this is, I was not. I still have not figured out how such a change would bring diversity, but I can imagine very well that things might get even worse.
Edit:
In case its not obviouse, yes, I like diversity too. Sure Id like to see more than 2 bows in the game, my only complaint is not to nerf the useless bows again but buffing them instead, which I doupt would be the case after such implementations.