Sleep timers are to high for PVP, 30 seconds of being frozen followed by 15, followed by 6 when you are the only one capable of doing anything about it isn't really good. You can't cross-class esuna and the one for SCH is only for their job so in a 4v4 with 2 DD, 1 tank and 1 healer, the only capable of removing other units enfeebles is the healer. Eliminate the healer's ability to act and you can pretty much terrorize the rest of the party.

Another simple fix would be to add a pvp action that works like esuna/leech to allow the DD or tank to remove enfeebles on the target so that sleep spamming woudln't be an issue.

Or they just limit sleep effect to a 15/10/5 seconds duration, cutting it in half be more than enough to help out since pvp itself is a fast paced event, the fights don't last longer than 5-10 minutes for the most part so if you are able to knock a person out for nearly a minute it does influence the chances of winning.