you are ignoring scaling.
its not that they are going to be god tier, its that they are going to be too cost efficient and too flexible
sappers cost nearly 2/3 the price of tommies, which means increased map control, which means resources
they also benefit from bolster which means 25% more health and firepower (although the benefits of an extra man are far greater than 25% because increased models means increased targets, which can lead to less damage concentrated on singular targets)
they also iirc have a 0.9 target size, which is below average making em harder to hit out of the box
they also have a snare so you wont be able to aggressively punish them in the light phase
they can also get PIATS to they will scale into the mid late game as AT
they are also cheap per head to reinforce any captured weapon teams
they can also build forward heals, reinforcement and emplacements
they can destroy cover
they can lay mines
they can lay wire
they can also heal your armour
they have the potential to be a zerg rush that can adapt readily to what ever the enemy does to fight them.
it needs to be tested but it has A LOT of room for making the game realllly shiity.
good luck to spamming Royal Engineer until you get Heavy upgrade
like i said before. Royal Engineer not Fine-ish combat squad what so ever, Give them 3 LMG in late game to win 4/10 match against vet 3 MG42 Gren and get only 1% HP model left is stupidness.
Map control is one thing, but holding it is another. Sapper cant hold aganist any mainline inf in early, mid game (even with 2 brens). For every model trade, UKF lose more than Axis.