With 6-42mm armouring of a simple riveted construction the M13 was still very prone to heavy MG and anti-tank rifles as small as 7.92mm, I'd still feel much more comfortable in a nice armoured car which would run rings around it for speed and mobility and the 4.7cm gun is only hull mounted much like the Lee, so most of the time the M13 had to rely upon twin 8mm MGs in the turret and we're talking about 12mph cross country performance.
A Daimler, Humber or SdKfz 222 is still a much better proposition. Hell I'd take a jeep with a Boys mounted in preference. But even in the Desert these were often scarce so indeed notably Australian formations made use of captured M13 tanks in at least three tank squadrons.