Diamond hole saws will cut through anything if you don't destroy it first. The action is more like grinding a hole versus what we think of as cutting like into metal or wood. The diamonds on the saw are quite small. If you apply too much force, you'll tear them out of the metal bonding them in place. Since you're grinding things, the heat can also mess up the bit, so keeping it wet helps to keep things cool.
Many diamond hole saws do not have a center pilot bit. If yours does not, the magic is to first start the hole with the bit at about a 45-degree angle, using the edge, start to make a divot and slowly rotate the drill body perpendicular to the surface, otherwise, it will tend to skate all over the place. Another way is to drill a through hole in say a piece of plywood, clamp that in place where you want the hole, and use that to hold the bit in place and keep it from wandering.
If you keep the bit lubricated and don't apply too much pressure, it can last quite awhile. Otherwise, you can ruin one quickly.
