Weiley31
Legend
The thing with the 5E "Gish" is the fact that it's "there" but it's pretty much spread out over multiple aspects within 5E itself: Namely via the Eldritch Knight Fighter, Forge Adept Artificer, Valor Bard, Hexblade Warlock, and the (Tashas) Bladesinger Wizard. Of those, a number of people/posters have mentioned that the Forge Adept Artificer (okay okay I hear you all official book only peeps grumbling in the background) is perhaps the closest thing to the concept in 5E. At least it's a whole lot more closer compared to the others.
The Eldritch Knight fits the Duskblade more and gets the ability to spell/attack, but sadly near the end of its progression. Same with the Valor Bard as well. However, a lot of people agree that the Tashas Bladesinger Extra Attack change is better and fits the Sword in hand and magic casting concept of the Gish, even if its a Cantrip. So updating the Eldritch Knight/Valor Bard to do that would be a fix for sure. The Hexblade would feel like a Gish and its Hex Warrior feature feels in line with that, but the only sucky part is that your dealing with Warlock Spell slot limits.
Funny enough, in regards the Duskblades' Spell Strike feature, well believe it or not it does exist in some form within 5E: Via the Matt Mercer Blood Hunter's Order of The Profane Soul subclass. It is a 11th level feature(IIRC) called Diabolic Channel and it works exactly like the 3.0/3.5 Duskblade's Arcane Channel feature. Note: The Updated 2020 version of the Blood Hunter doesn't have it anymore in the Order of Profane Soul subclass features. So keep that in mind when looking it up.
geekandsundry.com
Link posted for simplicity.
And also in regards the Duskblade: Lore wise they use a bastardized version of Bladesinging. So The Duskblade overlapping the Bladesinger somewhat is on point in regards to that.
The Eldritch Knight fits the Duskblade more and gets the ability to spell/attack, but sadly near the end of its progression. Same with the Valor Bard as well. However, a lot of people agree that the Tashas Bladesinger Extra Attack change is better and fits the Sword in hand and magic casting concept of the Gish, even if its a Cantrip. So updating the Eldritch Knight/Valor Bard to do that would be a fix for sure. The Hexblade would feel like a Gish and its Hex Warrior feature feels in line with that, but the only sucky part is that your dealing with Warlock Spell slot limits.
Funny enough, in regards the Duskblades' Spell Strike feature, well believe it or not it does exist in some form within 5E: Via the Matt Mercer Blood Hunter's Order of The Profane Soul subclass. It is a 11th level feature(IIRC) called Diabolic Channel and it works exactly like the 3.0/3.5 Duskblade's Arcane Channel feature. Note: The Updated 2020 version of the Blood Hunter doesn't have it anymore in the Order of Profane Soul subclass features. So keep that in mind when looking it up.
Matt Mercer Presents the Blood Hunter Class for D&D
Since the release of the original Witch Hunter class, I’ve had some fantastic feedback from the G&S and D&D community at large! Being my first real attempt at a homebrew player class, it certainly had some kinks to work out. At the same time, I was feeling a little creatively stifled with the...

Link posted for simplicity.
And also in regards the Duskblade: Lore wise they use a bastardized version of Bladesinging. So The Duskblade overlapping the Bladesinger somewhat is on point in regards to that.