Hoglan is nowhere near as tight a drummer as Reinert for starters, and DiGiorgio is a good player but there are many better than him. Sean Malone's performance on Focus and Tony Choy's performance on Unquestionable Presence are two that spring to mind that are leaps & bounds ahead of the bass performance on ITP. Digiorgio also has a shit sound which doesn't help his cause. I saw them live on that tour and discovered why - he was using a Fender Precision fretless plugged straight into an Ampeg SVT 1000 with an 8x10 cab, no effects at all. That rig is great for a classic rock sound with a fretted bass, but fretless needs some work to sound good, especially if you're going to try to use it in a heavy band setting. It's no wonder the bass was buried on Human.