I haven't played with everything yet but ...
Alchemy- Seems pretty balanced, it's actually pretty hard to make a super-potion more complicated then a long duration/potency one, and it takes a lot more effort & resources then vanilla.
Altars - Seem well balanced, if anything I'd say it's actually a bit too hard in the Tier 1/2 range to craft many things because you can't use many runes. Tier 3/4 seem completely fine, haven't tried Tier 5 yet because I haven't killed a bunch of Withers.
Tools - Also well balanced, The bound sword seems to be the strongest weapon in my pack, but only just barely. The other Bound tools are crazy good, but so dangerous I only ever make the pick, and then I rarely (and Carefully!) use it.
Armor - The blood armor set actually feels a bit strong compared to the rest, but I've never used MPS or Quantum armor either, and not excessively so. It's actually frustrating you can't put flight into it somehow, but I believe that's on purpose. Void sigil in the armor doesn't seem to do anything (I thought according to Ako it removed Void fog), but the rest are good.
Sigils - Again, totally fine compared to say Thaumcraft Wand Foci. Actually compared to them, (most) Sigils feel a bit weaker. (Blood Lamp vs. Lightning Focus, Air Sigil vs. Uprising Focus, etc).
Rituals are awesome, and definitely as much investment as other magic mod equivalents (or more).
Haven't messed with Spells, mostly because the new ones are so complex to craft (and not documented yet), and I don't know why I haven't tried the older spell system yet.
Haven't tried the Well of Suffering thing yet, so I can't comment on how OP/not-op it is either.
All in all, it doesn't seem overpowered, and it does take a lot of investment and work to get most of the "goodies". It's actually a slightly better set up of a magic system (for me) then Thaumcraft, just because I enjoy building structures and collecting resources more then I like research.
What the heck is "zerging" in this context?