AAAA	BBBB	CCCC	DDDD
	0	350	0	245

And actually, let's check that Excalibur doesn't use your WORST combat stat; making my main character have 255 AGI didn't help, but let's go for the 255 omni.
	0	262	0	246	; if omni-255 still can't bust 32 defense, yeah, there can't be even a really stupid stat modifier here to explain those 10s.

No, no wait. Theoretical max before mitigation damage is 16, what if it scales by an additional (worst stat/256)x? Could get a spicy 31.truncated into block there. Okay, gobbo, it's time for you to have 31 defense--
	0	223	0	248
	0	189	0	246	; okay, bump down to 30
	0	267	0	250
	0	352	0	248	; 25
	0	269	0	257
	0	229	0	256
	0	195	0	257	; 20
	0	277	0	266
	0	362	0	264	; 17
	2	277	0	269
	3	237	1	272

Now remember, if RAND was significantly over 2 we'd see swings for higher than 400 from the hammer eventually. Let's bump gobbo to 18 defense:

	2	202	0	270
	0	279	0	269
	0	364	0	273
	0	276	0	273
	0	236	0	274
	1	202	0	275
	0	279	0	278