I think I'm getting a handle on your situation now; am i right in thinking you just use the 17-40 and 70-300, and you were using the latter as it is a better 'portrait' type lens ?
Yes, that's right, certainly better as the 17-40L ... I only recently moved to ff and used the 17-40L on crop as a "normal" zoom. Alas, "pro" doesn't just mean spending money, but also earning it and make do what's availabe?
If you are going to shoot these types of pictures I would strongly recommend you get a fifty of some sort; the 50/1.8 is the cheapest way in.
I had that until it broke after it fell down (100% plastic) but I hated it as it's so soft and has a horrible bokeh. I also have to admit that I currently feel that for two models (pet & person) I can do most things @70mm other people might use a 50mm for because they have it in the bag?
It's not just a case of 'what you have in your bag at the time'. If you need to produce a certain type of shot then you must be able to achieve it, more so when you are being commissioned to do so. There is a significant difference between 50 and 70.
I know what you mean about the 50/1.8. My other suggestion for maximum cost effectiveness is the 40 pancake. This lens has a very pleasant bokeh in many instances.
If you are shooting again tomorrow I suggest trying your 17-40 at 35-40 @ around f4 - 5.6 depending on what is going to give you your 0.5 -0.7 m dof that you are looking for. I think you might be surprised. When you look at agierke's 35mm shot at 1.4 there is no problem with lack of compression, in fact it is an excellent picture. You are going to be in a different orientation and closer and not focusing on a single pane so you'll need to use a smaller aperture. Remember to try and get a focus point fore or midway of your dof range.
Post what you get, I'll be interested to see.