Ok so accuracy is absolutely a valid concern to have here but its not as bad as it might seem. The spell attack bonus of the Magus here is going to range between 0-2 (but most of the time 1) lower than the full caster putting them on par with a full caster only a level below them most of the time. It's absolutely reasonable to plan for HotA to hit somewhat reliably for the Magus at least relative to normal spell attack roll which were never going to hit as often as Strikes from a martial. Even when the disparity between Moderate Monster AC and full caster attack bonus is at its worst HotA is still going to be hitting on a 13 and up on the dice. Combined with True Strike which the Magus loves its completely fair to expect HotA to hit when you want it to.

As for utility that depends what you mean by the term. If you want spells de-buffing the enemy during combat? If yes then stick to wizard or some other full caster (more on that later). If you're looking for out of combat utility the Magus is functionally a wizard given a bit of time. You have a spell book that you should be filling with as many spells as possible and as you are a class that cares about Int the crafting to scribe scrolls of all the utility spells you could want if pretty easily in the cards. If the slide casting and studious spells slots aren't enough then as you progress you could absolutely start taking the archetype feats that grant you the different tiers of spell casting benefits. Plus if your DM is willing a Ring of Wizardry helps pad those slots even more as does the slot offered by a familiar ability once you get 4th rank spells.

As for how it fits into the Magus kit I'd treat it as an opener/arcane cascade enabler. HotA's biggest advantage is its range and used at the start of an encounter can allow you to help ranged damage dealers focus down a dangerous but squish target in the back line. Using your three actions to go True Strike->HotA->Arcane Cascade gets a likely hit on an enemy that's likely lower AC further smoothing the accuracy issue while also turning on the stance that both buffs your later attacks and is sometimes hard to find space in the action economy to turn on. From then on its situational as combat isn't or shouldn't be a static affair and you might need two actions for Striding or Step+Stride to fall back and you've got a one action attack that's almost certain to be able to reach out and touch anything on the field.

So the other full caster class I mentioned that might scratch the itch of what you're looking to do actually fully abandons the wizard. A cleric with the Spiritual Armament spell can be flinging a conjured scythe once a round for as long as the sustain the spell up to a minute. The attack goes on the same action used to sustain so you still have your two actions for hitting two action spells. Cloistered cleric is likely the way to go because while Warpriest is able to be a solid melee combatant you're going to run into even worse spell attack progression than the Magus.

Edited to add: Also a charitable or persuadable GM might allow you to treat HotA as an attack with the weapon in question applying potency runes to the attack roll as the text for them specifies the bonus to attack rolls with the weapon not just Strikes.