These perks are simply basic. If you intend to lean on your Destruction magic at all, you simply can’t afford to skip these- they make you vastly more efficient both in and out of combat. There’s really not much more to say here.
Destruction Dual Casting-
Whether or not this is worth it to you depends on how, exactly, you fight at any given moment. If you can manage to keep attacks off you, whether by annihilating their source (especially easy when using the perk to begin with) or letting your follower take all the heat off of you, then this is valuable- if you are often taking attacks, though, you are probably a lot more interested in keeping a defensive spell in one hand so you can keep yourself alive. It’s worth noting that this isn’t the most flexible perk either: you can only dual-cast while wielding the same spell in each hand. Not the most crippling drawback, but it does trade in some of your versatility for that power. One final note- if you intend to use this perk even some of the time, make sure you keep as many of your spells as possible on your Favorites list, so that you can swap easily mid-combat. Failing to change out spells at the right time is horribly crippling.
The Destruction perk tree isn’t that large in terms of the number of perk points you can put into it, so if you’re leaning on your Destruction magic there’s very little reason not to invest the full six perks in maximizing these three perks. Frost and Shock spells are both a bit more specialized than Flame spells- where the fire is all raw damage, cold damage also affects Stamina and electric damage drains Magicka. Because of this, unless you have an especial hate for spellcasters or face a lot of foes that like to run away, you should probably invest in Augmented Flames first. The exception is if you’re trying to use sneak ranged attacks as a spell caster- doing this works best with Frost spells since not only are there more projectiles in Frost, draining Endurance works a lot better if you do it before the target reaches melee range.
This perk notably only affects the single-fire spells, so don’t expect your channeled effects to lock an opponent down with a continual stagger. It also only works while you’re dual-casting a spell, so if you’re not spending a lot of time on dual-casting, you probably won’t find this perk nearly as worthwhile. That said, the ability to slow pursuers is vital if you’re a squishy robed mage. Try to also keep in mind that some enemies are resistant to staggering, and won’t be as affected.