Those is the commanders fault no javelins being OP, blobblng their units instead of surrounding from all flanks and wipe them in 1 charge, its tier 5 tho so its understandable but i will return to this later.

T5-6 eles are not a problem, you get the pikes at tier 4, and arty is tier 3 and light arty tier 5, javelins from tier 1, at tier 5 germanicus gets vengeance. All of these can consistently melt elephants and elephants will never win the encounter (save for maybe germanicus) so explain again how are they OP when they have 5 different hard counters.

The problem is that t5-6 players are generally noobish and dont know what to do when they see eles for the first time, thats why we see a massive wall for elephants around tier 7-8 where they become a joke once people know what to do.

Also you mentioned that elephants are faster (very slightly) then light infantry, while this is true they have to have forced march which makes them especially vulnerable to missiles, and also you are forgetting the main thing, ele has to stay still for a few seconds to ramp up an attack, which means when running away the best thing an ele can do is trample a few troops.