[1.2.339] Lionheart Castle?

No, the correct information is that Magic Boost really raises attack speed by 2 levels no matter the skill is at which level.
Not only what I have mentioned before, lots of I/L and F/P Archmage's skills are attached with damage over time (DoT), additionally, it is effective to bosses and each every different Dot (including Dot of each every poison and ice elemental skills) can exist together to one monster. It is another big blow to Bishops.
You said a Bishop is supposed to help others, but do you know that no one has obligation to help others without any feedback. It feels very bad like we Bishops are slaves.

Why is there always someone complaining about Bishops not being on par with a Damage dealing class in terms of DPS?

If you dont like a supportive role of a Bishop and want more DPS, here's an idea, make an Archmage. Bishops will never die and will always be wanted in parties, and come with training speeds on par with the other magicians. Not to mention high survivability and still rather decent DPS for such an supportive class. It highly depends on your equipment these days anyways, a well-funded Bishop could easily out damage a Corsair, let alone an lolArchmage.