I think the missing Deftones track is "Tempest"
I think the Toto tracks are "Better World" and "Jake To The Bone".
Is there a criteria for asking for a letter? If not, I'll take an "S".
It's not Tempest, folks!
The Toto and CHVRCHES guesses are correct. This might help with CHVRCHES: Note that wherever a slash is separating two distinct songs, I put a space on either side of the slash.
We just guess a letter whenever anyone wants to see another. Here's the S:
twosuitsluke: King Gizzard and the Lizard Wizard - Robot Stop / Magenta Mountain / S___ _am _
Deftones - Swerve City / Entombed / __m_e__
romdrums: Toto - Better World / Jake to the Bone
A_t_m_ - A_t_t_de / __d F_e_
Lethean: Katatonia - Evidence / Lacquer / Neon Epitaph
VOLA - Applause of a Distant Crowd / Smartfriend / Inside Your Fur
____ _r_ms__ - Fa__e_ A__e_ / E__ta__
kingshmegland: Mile Marker Zero - T_e Ar___te_t / ____ / _r__a_a_da
__st D_ma__ - S__e_t _r_ / R_se _f _s__as_
Dead Letter Circus - The Mile / Here We Divide / This is the Warning
__a E_____d - B_ae_ma_ / S__ A_d T_e M___
Cyril: CHVRCHES - Leave a Trace / Science/Visions / How Not to Drown
S_eet B____ ____r_m - _a___s_ / _e Are T_e _r___t _ar_ers
T_e __ber_am - __ Sa__t_ / T_e M_ra_ _a_ds_a_e
T_e ____ers - _est ____s / R__a_a_ __rses / __ T_e _ar __ts_de
Se_e_ S__res - T__s __d _s Dead / B_r_ ___
wolfking: Angel Dust - Bleed / Cross of Hatred / Freedom Awaits
Stadler: Concrete Blonde - __e_ / __tt_e ____ / ____ab_e
Letters used: D R T E F M B A S
Note that I've also added an "a" that I missed earlier in the third King Gizzard song.
Edit: Also just added a "t" I missed in the 13th artist name.