Its resists really don't matter that much at all, as its bulk is so pathetic, any reasonably strong neutral hit will OHKO it. Ghost resist is largely irrelevant, as its not a common attacking type, and the pokes that use it have good coverage moves that can OHKO Heliolisk. It's speed tier is also largely irrelevant, as the only notable thing 109 speed can do for it is outspeed Keldeo, while it's competition, thudurus i, mega manteric, hell even jolteon, outspeed it anyways.Heliolisk isn't anything like the other Electrics. It shares a STAB, but its speed tier, type coverage and resists are all different.
If you want an electric type with interesting resists (and bulk to back it up) rotom-w is the way to go. It basically walls every important type heliolisk resists, with added ground immunity. This is at the cost of a grass weakness, but grass is an extremely marginal attacking type anyways.
This, is why it was rejected an OU analysis. Still hold that it will be decent in UU though.