AoE indicator would be a godsend for lower rank play. 

In the last 2 weeks, KT is the most popular (92.3%; picks + bans) hero in HL ranks Bronze through Gold (according to HoTSlogs) with a 53% WR. He's banned vs picked at a 4-to-1 rate, in TL he's still banned at higher than 2-to-1 rates with a 70%+ popularity. In Plat and above he's banned/picked at a 1-to-1 rate and is still the 5th most popular hero but is only has 50% popularity. 

What do I want you to get out of those numbers?   Higher rank players trust that they and their teammates know how to negate his living bomb damage by spreading out and aren't that afraid of him/don't need to ban him that much despite being up against much better KTs. 

Meanwhile in my games, players seem to think that getting lit on fire is an invitation to hug your backline allies/runaway to the fountain despite heavy traffic at the gate. This lets KT carry, despite the fact that they went Convection at 1 and are heavily invested in using pyroblast on Genji/Varian/Maiev. 

If we put some little circles around living bombed heroes, some small subset of Bronze/Silver might realize they need to stand away from their allies. 