Ampharos survives at least one hit from earthquake most of the time, giving it a chance to confuse the enemy with confuse ray (or inflict paralysis, if it's not a ground type) :V Quick claw can also help with inflicting status effects. If it has nothing to counter the type it's up against, you can just switch it out if the enemy's confused and send out a pokemon that IS effective against it.
Not to mention that Heliolisk heavily depends on TM/HM's to get moves that can cover its weaknesses, otherwise it only has 13 moves that it can learn just from leveling up, which are mostly electric/normal/ground. Also, dat fighting weakness so a pokemon with technician, mach punch and something that boosts fighting move power/attack would be a problem ヽ༼ຈل͜ຈ༽ノ
Ampharos is only weak to ground (unless it's mega evolved, but that won't be happening for a very long time jan hates me) and has a better learnset when leveling up, giving it power gem not too late at level 36, signal beam at 51 and dragon pulse at 65. Sure, it can't deal with as many types as heliolisk does when given the right TM's (of which the most aren't even available yet with the exception of surf), but the moves it can learn are stronger for the most part, and overall is capable of dealing more damage attack AND sp. atk wise+being able to resist more. its bulkiness makes up for it being so slow, but even then that can be covered with a quick claw and some luck in it activating :V