I'm glad it's not just me! OK I don't have the big foot issue (US 10.5/EU44-45), but I suffer terminally from the wide forefoot/narrow heel issue. I haven't been cycling too long, but will offer my limited experience:
Shimano - I'm a 44 in length in a Shimano. But since they're so narrow (or just like most cycling shoes, I guess) - I have to size up to a 45 to get my forefeet in. Forefeet are hurting after an hour or two, heels are slipping all over. I can't walk in them off the bike, and can't climb out of the saddle either. I've had two pairs - RH-088 road shoes, and a lower end MTB pair that I still have. Neither of which are wide, which no one carries and I was told by two dealers that the wides aren't that wide anyway.
Bont - followed the advice of a few others with the canoe paddle foot issue, and tried out a pair of Blitzs. Used the foot tracing method, was told I needed a 43.5 wide. Had to jam my toes in, even after heat molding and using the butt end of the screwdriver method to make room for the forefeet, they caused miserable pain within minutes. Beautiful shoes, super lightweight, love the engineering, but even in wide my forefeet didn't fit the tubs. Maybe if I had a 44 or a 44.5? Then the length would probably cause heel slippage.
SIDI - this is the closest thing I've had to luck, though the heels still slip. First was my Tri shoes, the T-2. These are regular width I think (they don't say Mega, but they are fairly old), but were WELL used by someone else. They're not leather, but definitely felt broken in. Comfy enough I used them as my road shoes for a few years instead of my Shimanos which I ended up selling. Then I got a year-end sale a couple years back (LOVE Merlin!) on Carbon Ergo Mega 4s. Size 45, again, which is too big - but of course they didn't have a 44.5 and a 44 I had tried previously was too small. The Ergos have a heel adjustment screw to narrow the collar a bit. Not enough to eliminate heel slipping, but enough to keep them so they only slip when walking and not while riding. I'm also not throwing down sprinter wattage, so take that for what it's worth
Been wanting to try Lakes for a long while, but as always no one near me carries them and I'm hesitant to pay full price for shoes plus to and from shipping. Especially when my SIDIs are close enough for the time being. The search goes on...
(I had some pics of my various shoes up but apparently having less than 10 posts prevents me from doing anything)