I am pretty sure you will get ripped on. In med crator your going to get owned(unless you cannon, but you will be low hp, meaning you will get ripped on by dds'). So I suggest just go tank in PVP or BH.
Greater Demons for 55+, and zombies in varrock sewers(across the river) are good experience .. just attack all the ones that come in range .. its multi, fetches good xp if you know how to use the area.