Can't say I've really read the thread, and probably won't, but I'm going to drop some info on the Bloodmage Concept Because I'm bored and this seems like a good place to do it. I'm not going to really say anything towards the balance side of things, but rather, explain why certain things are the way they are.
The Bloodmage was designed to be a Highly Offensive based Healer. It was meant to be the "Wizard" of the healing archetype, while keeping his roots in healing.
If a Wizard was able to 1v1 a class in 10 seconds, the Bloodmage could accomplish it in 15-20. That is to say, he has decent damage output, and can hold his own against most classes, but it takes him longer to do so, and comes with larger risks.
Transfuse is supposed to be the bread and butter of his whole design, and also the promoting risk factor. The Bloodmage uses his Blood for all actions. How does he use his Blood? He Transfuses it into Mana. Simple, no? However the old Bloodmage did not work this way. The old Bloodmage spent his HP directly within the spell. When I made the design shift to rely on Transfuse for the concept, his Mana costs went up, and his health costs went down (or were removed entirely).
With his current design, a Bloodmage should be forced to Transfuse very frequently during EVERY fight to maintain this idea.
However, any class spending a large amount of their HP by converting it to mana, is sure to be put down very quickly. This plays into the risk factor for his 1v1 design. SIphonBlood is your main defense against this. It allows the loop to continue throughout the fight.
He is always putting himself at risk by transfusing. He is always sustaining his own HP by taking it from others.
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"The Blood Cycle"
Bloodmage A has full HP and full mana.
Activating a damaging ability reduces his mana.
Low mana means he must convert his blood into mana via Transfuse.
Bloodmage A now has full mana, but low HP.
Bloodmage A uses SiphonBlood, and how has moderately high HP, and moderately high mana.
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The above cycle can, and should, repeat several times throughout the fight. SiphonBlood allows him to balance the two out. The Bloodmage is using his own Blood to end your life, but your life is what maintains the life of the Bloodmage. Without this "Cycle of Blood", he should be very limited in his potential.
And that is the core design of the Bloodmage. He has high mana costs to force transfusions. However, he has a spammable heal that has a relatively low mana cost. The kicker, of course, is that he can only cast it in combat. He maintains his HP, and mana, via absorbing the life of his enemies.
So where does the rest of his skillset come in? Well, that's largely irrelevant. He can do it Inbetween the cycles, or it can be part of the cycle itself.
The idea is that he can spend his HP/Mana to do damaging or supporting type behaviors, such as healing, debuffing, buffing, or other misc concepts. However, he must constantly maintain his cycle in order to continually perform such actions. BloodBond is supposed to have a dominant role here. It exists to allow the Bloodmage to be supportive during his oh so selfish "Cycle of Blood". He cannot stop Draining life, and he cannot stop converting that life to mana. In order to allow him to help his allies in this unending cycle, he needs BloodBond.
Healing was chosen to be the primary function of BloodBond, but it didn't necessarily have to be the cast. Although, I'd argue that healing was the best way to implement it.
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So what about BloodUnion? Well, BloodUnion was really only something that was added to make the "Blood Cycle" more engaging. Doing something like forcing Transfuse to require BloodUnion, is somewhat silly for this reason. Such a change would halt the cycle, it introduces a kink, and it also slows down the progress of "Unleashing your BloodUnion". Which is a relatively large nerf.
If the Bloodmage is not playing similarly to how I described above, then something is probably not where it needs to be. If players aren't wanting to use BloodBond in pretty much every situation, then it probably needs tweaked too.
Just remember these things:
The Cycle should not be removed.
The Cycle should not be conditional.
The Cycle should somehow assist his allies, or harm his foes. (BloodUnion plays in here. BloodRitual / BoilBlood)
He should not be able to perform at maximum capacity without the cycle.
He should not be able to perform for extended periods of time without the cycle.
If he is performing heavy support tasks, it should hinder his offensive output.
If he is performing heavy offensive tasks, it should hinder his supportive output.
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The above ideas is also why his heals suck so much when cast on himself. A self heal bypasses the cycle. It allows him to sustain himself without forcing him into a transfuse loop. His Blood is his mana and his mana is his blood. Allowing him to obtain infinite amounts of both without the cycle is something i desperately tried to avoid. His true healthbar doesn't deplete until his mana bar goes with it. (Or of course if he's bursted down.)
(The above reason is actually why BloodRitual is useful on himself. It requires the cycle for him to even be able to cast it, so it's fine that he benefits from the ability almost as much as anyone else would. )
But yeah, those are the design concepts, and the reasons why some things exist. You may not agree with everything, but that's just how it is. Naturally, because I'm not really heavily involved in these things anymore, it doesn't have to stay this way. But if the balance team / coders wish to modify the class to a large amount, I would simply suggest to revamp the class altogether. His current playstyle relies on these concepts, and changing them is unlikely to produce good results. If you're going to keep the class as it is now, I would just suggest keeping everything I've mentioned in mind.
I agree with all of this though, as every bit of it is SO TRUE. 
