With regard to unit combats,
it's not the size of the dog in the fight, it's the size of the fight in the dog.

An animal's size is not going to correlate much at all to how much of a threat it is.
Secondly, in relation to how much food/hammers they are worth, and so as cetaceans wouldn't feel neglected, I compiled the following:
Orca: roughly same size as African elephant
Whale shark: 1.5 elephants (9 tonnes avg.)
Minke whale: roughly same as Af. elephant - actually slightly smaller
Humpback whale: 25-30 tonnes - 5 times African elephant
With the blubber, whales would probably give a higher proportion of hammers to food - not that blubber can't be eaten, but more of it is likely to be used as oil.
And then for comparison:
Mammoth: mostly African elephant sized
Hippo: 1.5 - 3 tonnes - half an African elephant
Indian or white rhino: 1.5 - 3.5 tonnes
Javan rhino: 1 tonne
Indian elephant: 3 - 5 tonnes: three-quarters of an African
And then if they are in the mod or will be in future:
Sei whale: 15-20 tonnes
Fin whale: 60 tonnes
Blue whale: 170 tonnes!
Sperm whale: 40 tonnes male, 11 tonnes female
Southern right whale: 40 tonnes
Mastodon: same as a small African elephant (4 tonnes)
Irish elk/megaloceros: half a tonne (0.1 African elephant)
Have fun with that won't you.