Thoughts/Perspectives from the viewpoint of:
A Jack of Too Many Trades (with appropriate training, of course)
Yes, re-inforce the area which will bear extra weight/stress by filling the void between the sleeve and the shank (Parallel thought is building up under golf club grip, taping voids and joints in fiberglass boat construction, or buttressing concrete forms).
You should dull the blank at this point to accept the adhesive - use fine wet/r/dry auto body sandpaper or very clean 000 steel wool to buff the area. Wipe area clean with tack cloth; follow with wipe of clean denatured alcohol. If you're using slow set epoxy, you may want to measure off the thread length you'll use first. You can soak this in the slow set to wet the complete surfaces of the glass fibers, then wind it on the blank.
You may also think about heading it on and off like a whipping - tag end under windings, end drawn under windings by tag loop. Be sure to oversize the (winding) thickness of the glass thread a bit, so as to create a bit of a press fit over the fiberglass bushing. A lot of rod manufacturers use masking tape to bush out the void in two or three places, then goop the hell out of it and shove the reel seat on. If you thought about doing something similar with the glass tape, it'd probably be overkill, depending on clearances between barrel of reel seat and blank face, but not totally outside the realm of possibility.