The main thing on seals is the housing needs to be like-new condition. If the outer bore is polished up, free of any schaffing then the seal is installed with grease on both inner & outer circumferences.
I never heard of RTV being used until I saw the DIY web vids; highly doubt a pro would do that but if it stops the leak why not? RTV isn't permanent but I would use accordingly so that excess doesn't make it into the gears.
Higher quality seal and remove/ install practice may or may not improve results. On this repair, remove the old seal without disturbing the housing and clean/polish bore then the install with seal lubed well so neither surface is comprised