Hmm.. Last 2 posts here quite interesting.. First we have 'LordHimmler' suggesting a range of stat ratios: Str

tam between 2:4 and 0:6, Patk

def between 4:2 and 3:3, and zero HP. Unless sig is missing some info, 'LordHimmler' doesn't play a Champion. Next is 'toudie' suggesting Str

tam of 4:2, Patk

def between 1:2 and 2:2, and 2x HP stats (the extra STR makes the Patk

def comparison a bit more weighted toward Patk than I've shown, but by a small-ish amount).
On the Str/HP question, I definitely side with 'toudie' that it's worth using: As reasoning, I have one of the top 10 (top 5 depending how you count it) knights on Artemis in guild. Not an easy thing outside PPK. He's currently statting Stam/HP both Hero AND Castle stats. He's got enough PDef and Patk, doesn't need more. Assuming a 80% shield form, the Str/HP stat for a Champion is more stam/HP than a Castle (completely ignoring the Patk from remaining Str), more HP than Hero and about 85% of the stam. I figure the same situation will happen for me a bit later, so using 1x Str/HP on all my pieces.
Not a fan of going full 4x Str though. Str has the advantage of switching between offense and survivability. And it gains from Hero Pot, Warlock buff, etc. where pure HP/Def/Patk do not (equal compared to Stam though in this aspect). However, in the numbers present on Bygone/Eternity, it falls short of both: Max 80% stam in shield form, and 252 vs. 315 (again 80%) Patk in normal mode. There's a portion of stats -- both offense and survivability stats -- that need to be present in both normal and shield form. So I want that portion at 100% -- ie, Stam/Pdef and Patk -- not Str.
Here's my current setup:
Stam/Pdef of Bygone, Eternity, Glorious
Stam/Patk of Bygone
Str/Patk of Bygone
Str/HP of Bygone
Another stat I've been playing with is Patk/Pdef Bygone. It's just so cheap. When I use it, it replaces the only Glorious stat. I think the Stam/Def Glorious may just be better, but the difference seems small. Definitely keep it under half my pieces with Patk/Pdef.
Stam/Patk Eternity would go fine in there somewhere. But it's harder for me to get and I don't see much improvement with it, so not even trying for that one.
Not endgame yet (newly 72, 5 pieces clean statted so far), so view may change over time. But I hope not.