Just got one of the 980 Ti's earlier today, direct from eVGA, and the card will not post on an ASUS X99 Deluxe.  The latest BIOS is installed, I've properly reset CMOS, and done all of the other usual tricks used when testing these types of issues, with no improvement.  
 
The board will display a "b2" Q-Code and the only output I can get from the card is the "Please connect the PCIe power cables for this graphics card" message.  
 
Power cables are connected and secure.  I have tried multiple cables and multiple outputs, including giving each power lead it's own cable, with no improvement.
 
All available PCIe slots have been tried, no improvement.
 
PSU is an SS-860XP2, so well beyond the minimum spec.
 
Two 970s (SLI), a single 780, a single 770 and an old 460 all work just fine on the board.  If I replace the 980 Ti with any of the listed cards, it boots right up.
 
So I figured, it must be a dead card right?  Nope.  The 980 Ti works just fine on a separate Z97 board.
 
Is this a BIOS issue similar to what was seen with the 980s a few months ago?  Is there anyone else using an ASUS X99 Deluxe with one of these cards?

Already on the latest UEFI version (1702), and re-flashed again with Flashback using a direct linked CAP file at ASUS's request.  No improvement.

As stated in the OP, yes.

Two 970s (SLI), a single 780, a single 770 and an old 460 all work just fine on the board.  If I replace the 980 Ti with any of the listed cards, it boots right up.
 
So I figured, it must be a dead card right?  Nope.  The 980 Ti boots just fine on a separate Z97 board.

 
 
I have another card en-route on Tuesday, as I was able to snipe one earlier today.  If the new card works, this is an eVGA issue (or the card is actually faulty).  If it doesn't, it's clearly an ASUS issue to fix with a UEFI update.
 
I should also run the card through some tests on the Z97 to see if it shows any other signs of failure.

Yeah what bcavnaugh said.........................
 
I ran into a similar issue when installing a new Plextor M6e BK 512Gb PCI-E SSD on my Asus RIVG X79 ROG mobo as I had changed the CSM from the Legacy or UEFI setting to UEFI only & all subsequent settings under this to UEFI 1st before installing this PCI-E SSD (was advertised as Legacy\UEFI compliant) then my box would not start as I got a POST message afterwards saying that this was out of order & no boot drive was installed.
 
I finally figured out that the CSM had to be initially set to look for Legacy OPT rom & UEFI (CPU & mem still use legacyOPT rom protocol so they initiate CPU 1st, mem 2nd) then set all else under this setting to LEGACY 1st then all went well after that once the Win 7 install installed the UEFI protocol on the new PCI-E SSD then went back in the Asus UEFI & reset all settings under the initial CSM setting back to UEFI 1st (UEFI protocol takes over after the CPU & mem initiate...thus why the initial CSM setting has to be set as LegacyOPTrom & UEFI then after this all other settings can be set to look for UEFI 1st).
 
Now if you have already did this then I would give EVGA a call as well as Asus & inform them both of this issue as this could be an issue in Nvidia's UEFI protocols used on this new vid card not being recognized by the Asus UEFI being used on this mobo as the 970's are using Nvidia UEFI as well & they test as working.............................
 
Just a thought..........................
 
<salute>

Dr.Doofy
Yup, did all of that already, as well as disabling Secure Boot/etc.   That usually addresses storage boot device issues, and the board will still typically POST in those situations.  I did it anyway just in case, same result - b2 and the power cable message.
 
ASUS support is already deflecting to the QVL, which is from March and only lists an eVGA 760 as being compatible, so it's looking more and more like their problem to fix.
 
I'll know Tuesday, if the new card doesn't work it's clearly an ASUS issue.  If it does it's eVGA, or I just got a bad card that is failing in an odd way.

Hard to believe that your X99 Only supports GTX 7xx Cards.
They are in my Book Causing a Lot of Issues with EVGA Graphics Cards to the Point they are doing it only to piss off anyone who owns an EVGA Graphics Card.

What reference card manufacturer was it, and what BIOS version is on the hybrids?
 
I'm expecting (hoping) that this ends up being the case when the other card shows up tomorrow.

Did all of that too, including multiple flashbacks to different UEFI versions / setting changes.
 

I have tried multiple cables and multiple outputs, including giving each power lead it's own cable, with no improvement.

 
It's literally a situation where the 980 Ti is the only card (out of 5 tested) that won't work on the board.  I'll know whether or not it's this specific card / model causing the issue on Tuesday.  If the second card has the same exact problem, it's highly likely that the problem is something else.    

New card showed up from Newegg, and as I expected, it works just fine.  Chalk it up to a card failing in an odd way I guess.
 
Unfortunately, I have to eat the 15% restock fee.  Apparently eVGA charges that on all refunds even if the product is defective.  I certainly understand shipping not being refunded, but I guess they'd prefer to keep sending out cards instead of a full refund.  
 
Oh well lesson learned, Amazon or bust.

Correct, as part of the unknown problem was whether or not that specific model / vBIOS was the issue.  It would have been especially frustrating to end up with two of the same cards that wouldn't POST.  Knowing that the first one wouldn't, I tried a different model to reduce the chance of that happening.
 
It's also the first card I've bought directly from eVGA in a long time, as I was able to snipe one when it was in stock last week.  I wasn't aware that they charge the 15% regardless of the reason for the refund.  It'll end up being a ~$130 lesson to stick to Amazon.
 
Obviously they'd send me a replacement, but I don't need a second one.  I could take the RMA and sell it for full price, but I wouldn't screw over the buyer like that, as they wouldn't be able to register the card properly.