An easy way to increase the weight on your bar for this is to just load your bar evenly for the warmup set (say, 30 lbs) and then for the heavy set just slip another 10-20 lbs over one end, without even removing the clip. That end is lifted, and I don't think its unsafe to do during this move. (When you switch to the next exercise, you'll need to even out your weights, and make sure you secure them with the clip!)
Sometimes I do skip the warmup set. I can't remember if this is the first back exercise after the warmup in PS, but if so, I'm sure Cathe uses that warmup set to do just that--warm up the muscles for the HEAVY weight you should be using on T-bar rows.
PS
Another tip on this exercise, if you aren't feeling it, is to use a short towel rather than your hands to hold the bar. I do this, and I really feel this exercise in my back.
Hope that helps a little!
Wendy