Pierce holes will always be wider than the cut kerf. That is one of the reasons you use lead-ins. The concept is to pierce in an area that falls out. Cutting decorative plasma with CAD is a slow and challenging process. In decorative cutting you have to be able to easily import vector clipart (EPS, AI, WMF). High quality vector clipart is available at www.vectorart.com The clipart available in DXF is limited and hard to edit in conventional CAD. The other challenge is dealing with text. Not just sticking in a line of text but being able to wrap it around a circle or along an arc. You need to be able to quickly weld objects in the drawing and fix text so the centers of letters do not fall out.
You have great (and expensive) tools but you can do a lot more, faster, with a copy of CorelDraw X3 and the low cost SheetCAM that allows for plasma specific parameters. Trying to cut and sell dozens or hundreds of the same design puts you in competition with China and Mexico. The real profit in decorative cutting is to do custom and one-off (personalized) designs. That requires you don't spend hours designing or setting it up.
You need to master the drawing/artwork side of the equation. The cutting part is easy.