The biggest concern if venting between the shower and the toilet.
The shower vent will also vent the toilet, but normally you like to see the vent come off at a 45 or vertical and not flat.
You may want to at least roll it to keep it above the flow line of the shower waste line.
If you have other bathrooms coming down that line, then the lav woudn't really be venting the toilet.
I vent before a fixture enters a waste line.