If you put it all together it seems like a lot. However every Israeli brigade has an engineering battalion, and there are a lot of brigades if you include reservists. Wikipedia (yeah yeah) says 175+, but doesn't specify if this is active service only or includes reserves/stored vehicles.
Israel also uses their combat engineers a lot more proactively than any other army that I can think of so the need for a lot of engineers and replacement vehicles to account for attrition (in a potential multi-front war) should scale.
650,000 troops, 2,200 tanks and 5,000 APCs , most of which are ready for use within days or at most weeks and 400 bulldozers doesn't seem like that much of a stretch anymore ...
On a sidenote I wonder if Israel will be upgrading more Merkava 3s to 4(M) standard because of the war. Downsizing the tank fleet seems unlikely so it's either upgrade the old or build more Merkava 4s.