The bottom part of the quote was exactly the example I gave earlier about how drk could tank, especially if one of the title bonuses you could choose was enhanced absorbs, or drains.I think there should be some limits to how much customization gets done at the title level. If you start creating too many paths/specialization within titles, the game starts to lose class/role definition again. Like, to take WOW's system for applying talent points, instead of having three full branches/specializations to choose from, they could compress them all together into one "chart". They could have certain abilities dependent on others like in that system. You might be able to specialize in being a "blood tank", but it should be in a more subtle way I think, like maybe there would be abilities in there that boost your drain or increase your magic defense and you could take those over stuff that boosted your magic potency or stuff that increased your ATK, but lowered your def.
I think they should always let you be able to use abilities that you learned from other weapon classes and not mix abilities between titles. I think it get's really messy if you switch it around and have classes not mix, but titles mix like I think Anathiel was suggesting, because remember the weapon class spells/abilities are supposed to be the "generic" stuff while the title is suppose to give you the "specific" stuff. If you have WHM/CON not able to draw on abilities from THM or other classes, then you're really limited that combination because CON by itself isn't giving you as much generic spells that can be used for healing because it's balanced with stuff for buffing/debuffing and nuking. The whole idea of the title is to have something to map those generic abilities that you learn from your weapon class onto something with more definition like a job.
You might not like the idea of having a DRK being able to use CURE, but with the whole compounded penalties/affinity system a DRK/GLA that wants to focus on tanking, is only going to be able to use a nerfed version of that spell because CURE won't favor DRK or GLA, this encourages a DRK/GLA to use other means of healing, namely his drain spells, and reducing enemy ATK with stuff like BIO and absorb skills.