I bfeed both of mine so did all the feeds, but both were windy boys and it was never a case of just feed, wind and sleep. It was a case of feed, walk the floor with them for 2 hours trying to get wind out of them and stop them crying, then feed again then sleep. Then 2 hours later the same schedule.
Because of the legwork involved, DH used to share in the night settling and winding for every feed (but he has shorter days than you, up at 7am and home at 4:30pm).
On occassions when it was just feed and sleep, I did (and still do) all of them and DH sleeps through.
So, for me, it would depend on how 'easy' the night feeds are. If its just a case of doing a bottle and them falling asleep, I don't think it's much of an issue if your DW does them all (at least during the week), however if there is a lot of night settling required then I think you should share some of the feeds (or at least the nightsettling part).
However, maybe the key thing is that your DW has told you she's struggling and needs help - maybe that should be the focus here and not whether tasks are being shared equally...