espeon isn't anywhere near b-rank. listing out its stats and telling me it reflects EVERYTHING that isn't a direct attack is irrelevant; most of us know what espeon does. being immune to status, taunt, etc. is cool i guess, but that isn't how you beat espeon so it's largely insignificant. the way you defeat espeon, unsurprisingly, is simple attacking. espeon cannot beat the most common stealth rockers in the metagame. tyranitar can crunch it, hippowdon can just eq on the switch, heatran can just lava plume, ferrothorn can just power whip. if you don't get the picture, it's that espeon's terrible defenses make it a terrible answer to hazards. espeon's typing doesn't allow it to provide any team synergy which simply just creates a suboptimal build. why use espeon why you can use lati@s which check several top mons and can defog? excadrill, zapdos, etc. are all far more reliable. defog and rapid spin are reactive moves, meaning that you are losing a turn of momentum by using them; however, using a proactive ability such as magic bounce on espeon isn't worth your while. it ultimately comes down to the fact that espeon cannot check any stealth rocker effectively and threatens relatively few mons with its terrible typing. terrible typing, coverage, and synergy just makes it a terrible pokemon. absol at least can pursuit lati@s, have STAB knock off, check aegislash, etc. that's an interesting niche at least.
espeon for like D lol
Espeon is not just for hazard setters. He's for anything that isn't a direct hit. Think of Magic Bounce as a variant of magic guard; if it doesn't deal straight damage, it'll do jack to Espeon. The only exception would be if hail or sand is up or if Espeon switches into hazards. Espeon works wonders against M-Venusaur and Sableye. Yeah, Espeon isn't particularly bulky. If the enemy predicts Espeon's switch in, then yeah he can get nailed hard. However, let's not use "prediction" as an argument because it works both ways. What if they predict Espeon's switch in, but predict wrong? Espeon's mere existence plays mind games on enemies. To set up hazards now or wait till Espeon is gone? Hidden power may have been nerfed, but it's still a thing. Ferrothorn wants to stay in on Espeon? Okay, he might get smacked with HP fire. Hippowodon wants to predict Espeon's switch in? Okay, EQ away and see if your prediction is right. If it is, great! If it isn't, then Hippowodon might've just wasted time on a flying pokemon.
No, Espeon is not the ultimate solution to all of your entry hazard woes. He's not going to be smashing through Tyranitar nor is he going to knock out Heatran (unless Espeon is carrying the odd HP ground, an unlikely sight), but he can be a nightmare for dedicated hazard setters like Smeargle and Deoxys-D. He can be an annoying bugger for defensive walls that can literally do nothing to Espeon except attack. Everyone knows that Espeon is immune to status, taunt, etc and that means they're not going to use it on Espeon... if they predict correctly. Will Espeon switch in on Heatran to predict the rocks? Will Heatran use Lava plume to predict the Espeon switch in? Mind games that you and your opponent have to play. Mind games that are high-risk and reward. If you're trying to take on Heatran head on with an Espeon and you don't pack something like HP ground, you're doing it wrong. Plus Espeon works on other things like Rotom-W's WoW, Skarmory's whirlwind, Thundurus-I's taunt.
Espeon provides a unique niche that can only be mimicked by two other pokemon; Xatu and M-Absol. M-Absol is a physical powerhouse while Espeon is a special attacker. M-Absol also takes your team's slot as a mega pokemon. Xatu share similar typing to Espeon, but is typically less offensive oriented.
While Magic Bounce is a great ability, Espeon himself is not dead weight. He may have sub-par typing, his bulk may not be great, and his coverage isn't fantastic either, but he's on a great speed tier and he hits fairly hard. His coverage may not be fantastic, but he has some options. Aside from Hidden power, Dazzling Gleam is also a thing, making things like Mandibuzz and dragons think twice before switching in.
Proactive moves are ALWAYS more efficient than reactive moves. The problem with proactive moves is that you have to predict correctly. Proactive moves are more efficient than reactive moves, but they're also less safe. Take for example your mentioning of Latias and defog. If you're using defog with Latias, you KNOW that there are already hazards on the field. Once you use defog, you'll know exactly what will happen, but as you said, you'll also lose momentum. For Espeon's magic bounce, you have to properly predict the Stealth Rocks. If you do, then not only would your opponent have wasted time, they'd have also done you a favor by setting up rocks against themselves, saving you time since you no longer need to set up rocks on their side of the field. If you predict wrong, you'll get nailed in the face. Proactive is more efficient. Reactive is more safe. Higher risk, higher reward. Also let's not forget that magic bounce does more than just bounce back hazards, it reflects ANYTHING that's not an attack. So if you predict your opponent to use WoW or taunt, or w/e, you can also switch your Espeon in on that.
Espeon for D rank? Lol no.
Why use an overly subpar anti-hazards Pokemon when you can use ballstastic Defoggers like Latias, who can not only force out threats with actually strong moves, but also remove hazards?
Because Espeon can simultaneously deny hazards on your side of the field while setting up hazards on their side of the field? Espeon actually has a higher Sp.atk stat than Latias and the only thing that Latias has that hits harder than Espeon's moves is Draco meteor.
The issue is that Espeon is so one-dimensional that everyone knows what it's doing on a team. Regardless if you run a shitty Defensive set or a shitty Offensive set, he's still there to half-assedly bounce hazards and that can be easily worked around.
Everyone knows what's Espeon doing? Okay... so is he the calm mind set or the dual screen set? Does he pack HP fire or some other HP? Does he have shadow ball? Dazzling Gleam? How about Baton pass, does he have that or some other move?
Seriously though, that's a bad argument. Everyone knows what Rotom-W is doing. He's being a bulky pivot that burns stuff. Does that make Rotom-W bad?