On our 40 Ocean, the d/h caulking was very poorly applied by Bavaria, with a lot of gaps and therefore leaks. I've raked it out over the last two winters and replaced it with MS polymer caulking. Some of the old wasn't adhering anymore either (if it ever did) and you could just pull out long strips of it. It took quite a lot of the stuff, but now the area is completely waterproof.
On the 40 Ocean with the teak caprail and (stainless clad) teak rubrail, it was sufficient to take off only the rubrail, which exposes the d/h joint underneath. This was not too difficult apart from a few stubborn screws.
The screws and through-bolting on the joint (from stanchions, cleats, etc.) is plenty strong to do the job, so I feel no need to add more bolts or glass the joint, both of which would be near impossible to do all around the boat as you can't access all the inside space needed without really destroying most of the interior.
The teak caprail just sits on the fibreglass and even if there are some gaps underneath it, they don't matter as that water cannot find its way inside - unless you have some leaky screws. None of the d/h joint screws were leaking on our boat, but all of the stanchion bolts and most of the mooring cleat bolts did leak and needed rebedding. This would be the first area to check if you haven't yet.