well, if one poison procs, and you barswap instantly, the poison on your backbar wont proc before 10sec even if it has a totally different effect.
all poisons are sharing an universal cooldown while each enchant is sharing its own.
you can have one poison enchant and one oblivion enchant to proc in the same second or two because of barswap or DW.
this isnt true for poisons.
ps: i dont believe they want to change weapon glyphs behavior.