I would say that is too much. I recently went through these very issues converting my Raleigh Gran Sport to a 6-speed with some new old hubs I picked up. First, a 137mm axle is fine for a conventional 126mm 6-speed. With a claw the axle has to be positioned asymmetrically to the right on the hub. The reason is because the non-forged dropouts are thinner but the extra length on the right is taken up by the claw thickness.

If you have much more than a mm or so sticking out past the outer edge of the DO on either side the QR acorn on that side won't lock down. The reason is that the space under the acorn has to accommodate the spring. That's why the acorn has a ridge sticking up around the inner edge. The spring is a spiraling helix so that it compresses flat into a single layer of wire. If you have too much axle sticking out past the edge of the DO that axle length plus the spring thickness will exceed the depth of the cavity under the acorn. When you clamp the QR lever down it will seem to get tight but will tightened against the axle on that side instead of against the DO.

One more thing. The reason those "new old" hubs were a problem is that someone had moved a spacer from the right to the left while re-packing the bearings. I can only guess why, maybe to get less dish while using a 5-speed freewheel in 6-speed spacing. Anyway, I had to move the spacer back. You never know what a previous owner might have done.