Firstly, supplementary voting would do a better job of ensuring a mandate — you still get a majority of the voters in order to win, just using ranked voting. Failing that, a full ranked voting system or a two-round run-off system would work as well.
As for the point about partisanship, 40–45% of a winner’s ECVs can be won by simply appealing to a base. The additional ECVs required are often won by a “lesser of two evils” calculation in battleground states, leaving these voters feeling trapped and without any real choice. Therefore, the EC doesn’t really do anything to stop partisanship, whereas a ranked voting system or runoff model would ensure that candidates truly have to appeal beyond their base.