When choosing equipment etc, you have to look at what it brings to the dive, not what it does for us on the surface. Underwater, I don't really see any harness being any more or less comfortable, thus the single piece of webbing will provide a secure fit and reduced failure points. The pain of hauling around tanks on the surface can be mitigated by the use of foam padding under the straps while moving the tanks (on the surface only), or by asking team mates to lend a hand. While I personally wouldn't consider the harness in question DIR, I wouldn't have any problems doing benign dives with someone wearing it. Where my concern would come into play is with more advanced dives, where the need to use non standard gear to mitigate the effects of an injury would concern me (ie just how bad is the injury and what are the potential consequences of it).