@Chaam: I'm with Kobe here. 3x Dark Confidant should be enough.
I would suggest a Disfigure, a 3rd Spell Pierce or a 19th land in that slot.

For the sideboard: This looks solid.
I would probably remove the Loam, maybe also the Clique.
Also I like to run at least one Envelop, in a list with no discard preferably two.
Other cards to consider: Diabolic Edict or a third Charm.

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@Gazoline: You really want 2x Bayou / 1x Tropical when you play Hymns.
If you don't own a 9th UBG fetch you could also run the classic 8x fetch 4x Sea 2x Bayou 2x Trop base.
Since you chose True-Name, you probably do want 20 lands, because you'll be needing both UU and BB.
First card to cut if you want to add that land is of course the 2nd Disfigure.
Last remark on the main deck: depending on your meta you may want to main deck a Liliana or Sylvan Library.

For the sideboard, I'd suggest something like this:
3 Spell Pierce / Envelop / Flusterstorm
1-2 Disfigure
1 Murderous Cut (your only Delve spell, so should be okay)
2 Marsh Casualties (you want to get these - just order them online, they are quite cheap)
1 Krosan Grip (I like this better than Pulse because it can get rid of Blood Moon, Batterskull)
1 Surgical Extraction
1 Grafdigger's Cage
2 Pithing Needle (this is for Miracles, Sneak Attack, maybe recurring Wastelands)
1 Sylvan Library
1-2 Liliana of the Veil /15

Other cards to consider:
- Vendilion Clique (good against any combo, Miracles, useful against decks where you have many bad cards)
- Dark Confidant (good against Miracles, any deck where you have lots to board out)
- Jace, the Mind Sculptor (some play one of these on side - it's probably fine but I never tried it)

Most depends on what you expect to face. Here in the Netherlands combo is very prevalent.
If you expect to face more Jund, Elves, Death&Taxes, you might want to run more removal or sweepers.
If Miracles is my far the most dominant, you need Confidant, Sylvan, Envelop, Needles.
Against Burn you want to max out on Disfigures, Hymns and add Flusterstorms and so on.
If Dredge and Reanimator are popular,m you should be fine, but a case could be made for a third dedicated hate piece.

Hope this helps.