Taking a quick break from work and wanted to flesh this out more with concrete numbers so we're not just talking hypotheticals here:

Use my light grid, St. Nick as main and friend fluffy as the base case and to maximize the appeal of P2W, let's make fluffy MLB and we're fighting off-element (on-element adds 45% elemental, which slightly reduces the appeal of additional elemental from P2W.)

With soul weapon, my base case elemental is 30% + 45% + 120% = 195% elemental. My assault is 150%.

Switching from St. Nick main to MLB fluffy main improves elemental to 270%, no change in assault, so overall change in dmg is (1+2.7) / (1+1.95) = 25% increase in dmg from fluffy.

Switching from St. Nick main to Hagith main drops elemental to 150% but improves assault to 210%. Ignoring exceed, defender and ascension improvements, this change alone is [(1+1.5)*(1+2.1)] / [(1+1.95)*(1+1.5)] = 5% increase in dmg from Hagith assault gain.

We're not done yet though. In a somewhat close to meta light team, you should be at a 3T burst cycle, and depending on how many red abilities you have and what your DATA is, the burst accounts for over half of the total dmg each cycle (without PF, PF actually often slows down the burst cycle too much.) To keep the math simple, let's assume the burst is exactly half the dmg of each burst cycle. Since we're not spacewhales here, let's assume we're not even hitting the 1 mil burst cap, so only the 32% exceed and not the 24% cap is relevant. 0.32 / 5 base SSR burst multiplier is a 6.4% increase in dmg. Burst accounts for half of total dmg, so this translates into a 3.2% overall increase in dmg - this is a separate multiplier from the 5% we got from assault since assault raises the dmg of everything. Multiplying the two gets us to 8% increase in dmg so far.

Now for the defender part. As a first approximation, let's assume that you're just another body to throw at a rag, so you fight until you die and let someone else carry the raid. If you have twice as much health, you will survive twice as long and therefore deal twice as much dmg. Hagith increases our defender value from 50% to 70%, which is a 13% increase in hp, which means we multiply our 8% by that and gets us to 23% increase in dmg - this is almost as good as the 25% we got from using fluffy as main.

Now, in real life situations, you don't usually fight until you die, and if you're fighting something like lrag where its OD just ends you regardless of whether you have an extra 13% hp or not it's not even relevant, so we have to discount the value of defender somewhat. I'm not gonna even try to put a number on that, but remember, I have ignored ascension so far, which I will also not put a number on, and unless you discount defender to close to zero, Hagith for my current non-spacewhale grid compares quite favorably to fluffy. Even if you say that defender is only worth half the value I computed, Hagith still boost overall dmg by 17% - two-thirds of what fluffy is worth.

P2W is a big deal, nobody is saying otherwise, but Olympia eido imo is at least two-thirds as big a deal as a P2W, which is still a pretty big deal imo. You have to assign very low values to non-assault/exceed skills to conclude otherwise.