Nope. For smaller ships, range and maneuverability are the primary dictators of survivability in end game fleets. Sunder survivability is better than a hammerhead in most situations do to having significantly higher range. Sunders don't escort capital ships. Capital ships escort Sunders. BTW, this is also why Manticores are considered viable in end game fleets while Enforcers aren't. Manticores have 900/1200 range base due to the large ballistic mount.
Ignoring the "viable Manticores" comment, Enforcers can have 1000 range with HVD/Maulers. So if all you care about is range, Enforcers should be better than Manticores, not the other way around.
Back when Escort Package first released, I tried Sunders with Autopulses(so 700 range) and they did... okay, not as good as beams, but the problem was Autopulse itself and not survivability.
HVD/Maulers have terrible flux efficiency, and the Enforcer is a low flux ship. Multiply that together for not much.
Also, if you're comparing 1000 range class ballistic mediums, then compare it to the ballistic large 1200 range gauss, not the large's 900 range high dps.
There's also the issue where the AI will use the burn drive to get well solidly in range to cover for it's low top speed.
Wait, you're talking about vanilla Manticores as viable? I thought you meant LP.
There's several examples of viable Manticores. Look at the stuff MisterG and BigBrainEnergy youtube channels have put out on lowtech. (gauss or railgun/heph or LAC/Hellbore)
Maulers are very flux efficient! Only 1.0 on the tin, but very good armor penetration and high accuracy makes up for it. They are low DPS per mount and DPS/OP spent, so they are really only good on ships with excess medium mounts/excess OP/no other options for anti-armor.
HVD are not particularly efficient on paper,
but because of their accuracy, in game testing has shown that their "real" efficiency and damage per battle is competitive with HACs. They have different strengths and weaknesses (HACs better in medium and shorter range, better in hardpoints, but just doesn't have 1000 range, HVD is usually better in turrets, has better hull damage, etc) and the balance between the two is a lot closer than it first appears. This is something I was wrong about in the past, where I'd underestimated HVDs.
In terms of flux: an Enforcer with 2x HVD, 2x Mauler, 1x Flak is comfortable in AI hands. Either the flux skill or the flux venting hullmod are a good idea, but not even really required. This gives it 350 kinetic and 240 HE DPS, with high penetration, at 1000 range (1200 with ITU, add more for skills if officering), so makes it a better artillery platform than the Hammerhead (which is just not a good HVD/Mauler ship). It spends a lot of its "spare" OP on those guns though, so can't afford too many luxury hullmods on top of high flux/cap stats.
The Manticore is better endgame because it can mount the Heph, which is
twice as much DPS/OP and DPS/mount equivalent than the heavy mauler. Alongside 3 LACS (which are something like 50% better mount equivalent damage despite being low DPS, and 2.5 times better DPS/OP), it has 300 kinetic and 480 HE DPS at 900 range (and that kinetic can be increased with investment), and it spends less OP on those guns which makes up the deficit between the two hulls. The 2 medium missile mounts are much better than 4 smalls.
The Manticore's crappy PD in that configuration (I am not a fan of canister flak and that's all it gets in max gun mode), worse defenses, and limited arc on the main gun make it more vulnerable, but as others have pointed out and I agree, endgame destroyers are protected by their capitals and so that doesn't detract from its superior firepower. 1000 vs 900 range is, imo, not enough to make up for the gun DPS difference, but I can see others making a different call there. The missiles though... even though it is hard to get max investment on the missiles without sacrificing guns, medium missiles are just really good.
The Sunder has similar range as the Enforcer thanks to Advanced Optics and Ballistic Mastery competing, but System Mastery + High Energy Focus push its DPS way out in front. Gold standard artillery for a reason!