The strange thing about destruction is that at the master spell level, spells are cast single-handed, although you must use two hands to deliver them. Also, master spells highest damage is 90 points. You would be better of using the lower-level chain lightning spell, and although it's only 60 points damage, you can dual cast for 120 dps. I use it whenever I can (and am not putting Lydia in the way of the jumps), and I can deliver it from about the same distance as a bow. It's really amazing the distance that spell goes. Together with stagger, and the perk that turns them into ash heaps when they reach 20% health (I think it's 20%?), makes it very powerful. Unfortunately, if you play at the expert and master level, it will lack some power, and you'll have to reach out and touch the enemy a few more times before they die.
If you are using two hands, then they are two-handed...and I don't know what Master spells you are referring to regarding casting, all mine require two hands.
I have one perk in improved damage across all three types of spell, that gives me 125 hp in the Master fire spell, and 93 hp in the shock spell per second (I can't recall the frost spell damage). Those are huge figures compared to what you get from an unimproved melee weapon. Now, talking in terms of damage scaling using the skills we are talking about, destruction vs one-handed, with no improvements through smithing or enchanting, then the base damage for any unimproved melee weapon will never match the base damage for a comparable destruction spell at the same quality level...e.g. The humble iron sword is comparable to the sparks spell...the spark spell gets damage per second, while the iron sword has to have repeated strokes as it's a one-hit at the time thing; The top level one-handed weapon is a daedric one...unimproved, they do not reach the same damage output as any of the Master destruction spells.
Certainly, one-handed weapons benefit from the first tier perks, for the cost of five perks you can double the damage potential of your weapon...for the same five perks you can access Master level spells as a mage...so my iron sword, doubled comes in around 20 hitpoints, while your 'sparks' type Master destruction spell is pumping out 75 hitpoints per second...Okay...so I pick up a daedric axe...unimproved, it's around 25 damage, doubled, that's 50, cool...I'll use two of them and dual wield for around 100 damage...the mage then decides to use the fire Master spell, and pumps out 100.
But that 100 has an area effect, so can hit multiple enemies, which my two axes can't. Now, we can argue that smithing changes the entire dynamic, allowing the melee player to boost the weapon damage potential significantly...true, but if we do that, then we should also consider that the mage character can use enchanting to reduce the cost of casting destruction spells, and boost both their magicka reserve and their magicka regeneration rate, in effect giving them unlimited spell casting ability for those spells. Now, perhaps my math and logic isn't so good these days, but it seems to me that if I am slamming something or someone with repeated 100+ fire spells, at no cost to myself, or with 75 damage per second, again with unlimited use, then the mage character has a distince advantage...and we haven't even considered what the 'impact' perk can do, effectively locking opponents at distance through stagger, all the while soaking up killing damage. And, we haven't even considered the bonus of the damage improvement perks....150 damage for area effect, or @110 damage per second is a pretty hefty figure, whichever way you look at it.
Edit: I just realised the anomaly with the damage figures: difficulty rating. No issue, it's relative across comparisons between one-handed and destructions skills regardless of the difficulty rating.