Battle Clerics are allrounders compareable to crossbow scouts - not bad not good - at the moment Rose PvP is dominated by specialists, Gunbourgs lead the singletarget DPS classes, followed by Katar Raiders - Launcherbourgs and Mages are awesome if you have a team that knows how to use those.
At the moment all classes are "legit" and playable* - battle clerics do exceptional well vs Champions and Knights their biggest weakness I would flag on dual Raiders.
If you think about playing a Battle Cleric this is the best time to start it - I expect with the next big Patch BCs becoming really good with the readjusted debuffs and Gem/Elemental System + most likly a buff to the defense/block system!
In general brain wins - if you spend time on theorycrafting, damage analyses and in general a lot of testing you can make every class work.
Edit: There are classes that might become better so I would hate seeing all Players switching to BC (god, I hate that class nearly as much as knight)....
Edited by iMatt, 19 November 2015 - 08:08 AM.