On a big dead one I try to get a long 1/2" cable or two about 2/3 the way up if possible and put light pressure (come along pressure). If the tree is solid I cut a 90 deg. open face notch and use your backcut as normal leaving a 1" + hinge to guide the tree down. Felling dead trees is not like felling live trees because the hinge on a dead tree may not function as the hinge on the live one does. If the tree is unsafe then I pull it over with cable or push it with bucket only if the top does not look like it might snap out. If the top looks bad then I pull it off with the cable instead of having it break out on its own with you underneath it then I push the rest of the tree over if it doesn't go over when you pull out the top.
The way you do it will work too but I don't like to get under a dead tree with a machine pushing on it. A 2" limb falling from 50' will put a hurt on you for sure if it does not kill you. I have had more than one tree impolde after nudging it with the bucket because the entire inside is rotten or hollowed out(thats why I try to cable them first). If you would try to put a face cut into this type of tree it would be on top of you! I look for the telltale signs of rot: fungus growing on side of tree, holes, animal burrows, etc.
Also I take a 3 lb. hammer and listen for a hollow sound.
These are opinions only and every tree is different so use your best judgement from case to case. There are some that just are widowmakers plain and simple waiting to put the hurt on you.
If I had my rathers I think that I would rather have a top hitting the cab than my head.
If what you are doing works then use your own judgement and be careful!