They should just improve all attributs by one instead of 'calling' it a buff. Just like the books in D:OS1 which changed attributes.
Do this. Just make it a permanent irreversible boost, and limit the supply of blood roses (they do not randomly appear in vendor inventories).
This may be a good idea and would certainly be clearer.
However it currently works like a buff not a boost and perhaps it is deliberate. You can't use it to equip gloves with a minimum finesse of 11 if you have not put any points in even if you have the elixir for example. You can however use the memory slots so I'm not really sure what the intention is. Perhaps the minimum requirement is to nudge people into making more rounded builds rather than just dumping all points into STR/INT/DEX
They are limited in number - there are only 3 so far (and I've never seen them for sale) so unless you put them all on one character it doesn't make much difference with all the stat improving gear you get later on.