Yes, it should; however Eraser can only access those parts of the host drives that the file system can actually see. If, by 'wipe the drives', you mean everything on them, you could consider removing the Raid array, then mounting the drives in a caddy, formatting them, and then wiping them. More work, but the wipe will then cover all but the sectors marked as bad, which are, by definition, inaccessible to the OS.
It would be quite questionable in the case of RAID-5 -- you lose some plausible deniability (if you had any to begin with) since by definition of a RAID array, your parity would be the XOR of the actual data, which would definitely mean you deliberately erased the file. Apart from that, I don't see any reason erasures should reduce security (not offhand, at least)