Updated 2018
If you want a responsive card-deck, use the visibility utils to force a wrap every X columns on different viewport width(breakpoints)...
Bootstrap 4 responsive card-deck (v 4.1)
Original answer for Bootstrap 4 alpha 2:
You can use the grid col-*-* to get the different widths (instead of card-deck) and then set equal height to the cols using flexbox.
.row > div[class*='col-'] {
display: flex;
flex:1 0 auto;
}
http://codeply.com/go/O0KdSG2YX2 (alpha 2)
The problem is that w/o flexbox enabled the card-deck uses table-cell where it becomes very hard to control the width. As of Bootstrap 4 Alpha 6, flexbox is default so the additional CSS is not required for flexbox, and the h-100 class can be used to make the cards full height: http://www.codeply.com/go/gnOzxd4Spk
Related question: Bootstrap 4 - Responsive cards in card-columns