This isn’t a “Legit tactic” it’s a map design flaw. The line of sight shouldn’t be there from the safety of the base to the first objective.
Everyone claiming that the team doing this is “down a player” and therefore more vulnerable is wrong for one reason: The sentries.
For the team without Marq sitting in the back, they have to push a wave of minions up into the enemy’s sentry, past their turrets they’ve purchased, and into their fire zone. Then they have to get enough damage on the turret (which is going to fire at them) and get the shields to drop…
They have to do this into enemies who know they don’t have to engage away from their sentry, they’re holding a defensive position with only a few approaches, and they don’t have to advance at all because they know their one player is constantly damaging the objective.
They don’t have to try to advance, they just have to sit and get a reset on their tank’s shields every once in a while (you know, like in between waves)
Could they man an effective push, moving from a defensive position into a more aggressive one? Not very effectively, but they don’t have to. They just have to wait for the first sentry to go down, and now they’ve got the lead, which means they can continue to turtle if they would like, or if they want to start pushing, they now have overshields pulsing on their minions.
Even if all Marquee does is get through the shields one time, and hit the Sentry enough to do one point of damage, if they can keep the shields up on their Sentry while turtling, they win. I’ve had plenty of games that came down to a point or two in a stalemate, because of how tanky players are, and because of how defensible their Sentries are.
It’s simple to fix this, stick something (anything) off of the structure in the middle out to where it stops the direct line of sight.
I seriously doubt anyone would intentionally design a map to allow the objective to simply be to force a stalemate while one player sits in absolute safety and pings away at the objective.