Hey I just wanted to offer up a couple of ideas on the problems you're having
with that vocal line.

When faced with a dynamic or frequency dependent issue, a lot of us tend to go
for a plug-in solution and with good reason; it is quick and usually gives good
results. This however a generalized approach and it overlooks one of the central
advantages to using a DAW in the first place namely - Total Automation. In the
hardware world, eq and compression tend to be 'set & forget' solutions. Often
times we carry this over into the DAW realm overlooking the fact that we can
manipulate every singe parameter of an eq, compressor or any other plug-in
parameter in real-time and with near sample accuracy. I really encourage you to
dive into the automation side of Logic. It is simply, fast and incredibly
powerful.

Try this: Solo the part and then find the area that is being a problem. Isolate
the region and set locators. Cycle the region. Next add a single band eq to your
channel strip. If you already have plug-ins rolling, place it after your main eq
and before any other processing. Hit A on your Mac keyboard to go to automation
mode. In the track header you will see a pull-down labeled Volume. Using this
pull down you can select the frequency and gain of the single band. Use
automation break points to to gently dip the problem frequency only where you
have the problem; literally only during the 300-400 msec that the problem is
occurring. This is similar to what a de-esser would do, only here, you have
total control over what's going on. If you are familiar with your automation
tools, you know you can copy and paste the data from one area to the others very
quickly and then tweek each spot individually. Using this method you can make
absolutely transparent corrections to only the problems spots leaving the rest
of the track unmolested.

Once you get this down, you will quickly realize what you can do with dynamic
automation of compression-eq to draw out breaths, selectively compress the
tail-ends of lines or create all sorts of wild effects. Give it a shot.