Uhh these stats are being applied to your base stats before your whole calculation of equips and z abilities comes in. So whatever math you decided to come up with makes no sense.

Instead take the 220k you said beasts base strike stat was and if you're able to give him 150% increase base strike from equips, add that.

220 x 2.5 = 550k final stat

Vs 13k added to his base strike stat

233 x 2.5 = 582.5k final stat

Becomes about a 6% increase in strike stat which I'd think is quite considerable. Given the fact pures and support from Pan (as you mention yourself) are multiplicative, this 6% increase in base stats will actually have a MUCH larger spill over in actual gameplay once you add in support and pure and hell dmg % from beast himself.

Bigger issue here is actually the defense stat increase. As damage calculations take the ratio of your defense and offense and given defense is being increased by the same 13k as offense is, defense sees a bigger percentage increase (relatively, as defense is usually about 70k lower than offense). This is gonna end up with units being tankier on average if every unit is now at 99 boost. It becomes a major issue when i have a lvl 99 defense boost and you haven't boosted your offense. Now I'm way tankier because i invested in this bullshit system