The point is, that their superior range is everything that makes them viable. They also cost a shitload of resources and come to the game very late.
So I think it their range advantage is completely justified.
I wouldn't necessary agree with you on this point. They have a lot of advantages beside range. I am using the spreadsheet made by Endeav for numbers so plsc correct me if they are wrong.
Elephant: cost 640MP 240F /damage 320 /penetration 170 /max. range 100 /speed 2.7 /acc 1
Tigar: cost 720MP 200F /damage 160 /penetration 154 /max. range 40 /speed 3.9 /acc 1.8
Other stats are in the spreadsheet. With this numbers I would gladly give it a bit more mobility in exchange for this range (2.5 times grater than tiger is a bit crazy IMO). ISU is not that OP because it has weaker armor and costs more, but just a bit smaller range would be good, at least IMO.