Well, ask and you shall receive...
Yes, I'm running 2 x Cor 15's on one energy bar (eb832). I also run a Cor 20 but that is not plugged into the eb832 but rather a wall socket. Since I'm a huge fan of the pumps I have 1 x Cor 15 running the skimmer, 1 x Cor 15 on a return line. The Cor 20 is the secondary return line with longest plumbing. Anyway this gives a sense of redundancy and also hot swap capabilities with the skimmer should the need arise to swap.
I have been running this for about 2 years give or take and have used a couple different methods. First was running them 100% as the tank was cycling. This didn't do much other than cause a sand storm and move water in circles between display and sump. Nothing was in the tank and it didn't require anything so I stopped.
Once I did the upgrade and moved corals into the tank with a few fish I had I ran them about 60% or so each. This worked and was good. I let this go for a bit then decided to add a pair of 1" sea swirls. In this configuration I altered the pumps to ramp up and down over time with the low setting 15% and the high 80%. Worked great. Created a nice left right movement but my sump water level didn't like it much and ATO and skimmer complained.
Next up I created a virtual outlet, named it tide, and let it switch to manage the percentage of each pump. This worked great. Sump was happy. Skimmer was happy. I was happy. In fact that is how it is running today.
Back to
@SuncrestReef point. No, this isn't ideal. I'm not running 100% on either pump but the proper thing to do is to add a 2nd eb832 and plug one of the 15's into there. In fact, this is exactly what I'm doing as I have a spare 832 anyway and have been meaning to set this up. It isn't used but I can connect the Cor 15 to it and it will add in another layer. I'm not using the plugs nor need them but they are there and it won't hurt. It also allows me to swap a bar if there is a issue.
tl; dr - I am guilty of running this way but you do need to pay attention to total load on the device. I do not have a lot other than the Cor 15's and a heater. Larger systems probably shouldn't and safer bet is as noted - spares are nice.