Il-2 drops 4 bombs (around 320 damage each?). A direct strike on Tiger will usally deal from 600-900 damage. While a Is-2 will take less than half damage from a stuka direct hit.
There are a few very important differences though.
1) the il-2 drop is a plane drop, it moves in from off map
2) the plane can be shot down
3) it will take longer depending on how long the distance is for the plane
4) there is the warning smoke
5) it's almost impossible to have 2-3 bombs on a tiger unless you manage to ram it at the exactly right moment and have the ram stun or manage to immobilise the vehicle in some other way
The stuka dive bomb was overperforming for its former price because it reliably always takes the same (rather low) time to land and there is no smoke warning, so it can be missed. The crit was quite crazy, due to the radius. Support weapons, like mgs and at guns had almost no chance to get out in time, even if you were fast to react.