Compared to ISIC and Toby, Ernest’s single target DPS is lacking, especially since his -20% damage nerf in the Winter Update. He’s still an excellent waveclear, naturally, but that’s because of splash.
Honestly every character has backdoor potential (this is me speaking generally from Overgrowth as it’s the most common Incursion map played). Certain characters are better at it than others, but all character can potentially backdoor and from different areas. The tunnel is a solid spot for characters like Montana, Marquis, Oscar Mike and Whiskey’s of the world. The ledge is a prime area of backdooring for characters who can leap up there like Benedict, ISIC and Kleese. The rest of the cast has a good amount of effectiveness in the sniper roost of the enemy’s areas with hit and runs.
The thing about effective backdooring is knowing your limits as both a character and a player. If it’s something you regularly employ and don’t have a good escape plan planned out, then you become food for the enemy team and cause problems. Sometimes back doors can mean the difference between a win and a loss. One time I was playing against a group that was one Montanna and the rest healers/support and we literally could not win without backdooring, they were sustaining each other too well to even get kills without us throwing everything we had at one character and it wasn’t worth the effort and time in the long run, so we started doing hit and run back doors spreading out on their sentry, since their only assault was Montanna, they couldn’t react to it effectively (so advice number one, in short, is recognize team comps, if back doors can be a logical counter to a team who you cannot beat by beating down the front door, try the backdoor)
Another example of backdoor would be at crucial points in the game. Sometimes the team comp doesn’t agree with you and thus you must rely on player experience and skill. @vagrantsun and I have two examples of this that I can think of in game
On one game his squad, with his Tobi, began to backdoor us because the team comps and player skill levels were just too even and they got the backdoor effectively and my team couldn’t respond in a manner that was effective and they ended up winning. In the other game, I managed to clutch a win (as the score was literally 2 kills from a tie) via a backdoor Benedict to destroy their sentry and clutch the win via score as they had already destroyed our first sentry before that. Sure I got triple stunned by Vagrant’s Tobi and Shadow Haven’s Galilea, but the timing was on point and it got us a win as I was the only one who died, still destroying the sentry while the rest of my team retreated to avoid giving up points that would’ve given them the game. (The examples here are player skill level)
Those are the two main factors when Backdooring. The hill top is largely ignored until the characters that frequent the area (ISIC, Benedict and Kleese) begin to abuse it, but doing it once in a while or at crucial moments can be extremely effective. One time me and @Nemosis327 backdoored and blew up a Sentry with Benedict and Deande while the enemy team got too aggressive.
A main reason people hate Ernest so much is that he can effectively backdoor from behind walls by lobbing his grenades over walls and hitting the sentry from (at least on overgrowth) where the single big shard spawns in the middle of the map between the tunnel exits. In Monuments he can cheese sentries from well beyond fair means and in Echelon he is absolutely destructive.
@vagrantsun it seems you’ve got some salt on your hands. Are you wrecking folks again? I miss those days
I never stopped. I still get hatemail every 2-3 days.
Ah the good old days. I’ve been going solo a lot now and it just ain’t the same. Randoms won’t help you out 99% of the time. U remember those times I would single handedly destroyed a sentry?
I remember that time on Monuments specifically, that comeback wouldn’t have happened without you buddy. I think the score was like 18-0 when we claimed victory like champions. I know I was Oscar Mike, trying to lvl him up.
Last time I got hate mail was from a Benedict who thought it would be a good idea to taunt me after killing me once when I wasn’t paying attention, I promptly killed him 5-6 times in a row and taunted him each time, his team surrendered via his call for surrender and he sent me hate mail afterwards. I promptly told him to not taunt superior Benedict’s followed by a screen shot of my Benedict stats at the time.
Then I grouped up wit Travis, Nemosis and the group and he got paired against us again. He quit before we even got to start
skill and smart go hand and hand. Sadly, so do bad and cheap. I know that this term gets overused, and I certainly do not mean it personally, but the people backdooring simply need to get good. They need to get better at the actual game mode, starting at character select. Then they need to work on basic decisions. Then they need to work on character proficiency. Then they need to work on doing all of the above better than everyone they know. Then they will NEVER need to backdoor.
I feel like you try the most interesting things this game has to offer
I love backdoor players with less skill than me, they taste delicious when they feed my team
Backdoor is a perfectly legitimate type of play. 
I try to find any way to use the tools I have, and there are so many tools in this game you can utilize that it’s actually kind of sad how people think only certain characters can do things…