jinton makes susano useless as the madara fight proved. plus onoki seems to be able to turn susano to stone by increasing its weight. since hes here with gaara, gaaras sand will be able to attack sasuke from below with increased speed. already gaara's shown even 5 susano swords dont affect his auto defence since the sand blocked it and he wasnt evne looking in that direction. he proved at the start of the war he can restrain people from below by using sand hands and karura's form.
genjutsu is the main danger. if one gets caught then onoki can make rock clones and break gaara out or gaara can use a sand clone and break onoki out. onokis already fought against the powerful genjutsus of uchiha madara so he already knows not to look directly at the eyes of heirs of his bloodline.
if amaterasu's cast, i think it will just hit gaara's sand armour, and then he can discard it and reform once its pulled off of him by his sand. same with onoki as he can petrify it and turn it to stone. onokis will power will probably enable him to break the genjutsus anyway.
as for sasukes chidori, i dont think gaara's sand is earth release, so he should be abel to form up a small pyramid defence, and then enlarge it. as long as he keeps sasuke away from him with endless sand tsunamis, he will be fine.
and with onokis golems backing up, they should eventually get an opening for the dust release long range laser version. no way are uchiha bros standing up to that. painfully, their stationary susano spam fighting styles are fatal against these two kages whove fought uchihas enough to counter them effectively