Every summons have its own database, mostly the skill damage %, but we have to consider some summon hit 2 times are not shown here.
https://tos.neet.tv/npcs?name=pc_summon&race=Velnias&cn=1&f=1
Templeshooter is really good, and it is best if you have at least Necro1 to have shoggoth apply the decay for you.
But of all things, it is dealing 217%x2 with 2s cd which is lowest among 2hits summon, but it become highest when you apply decay. Not to mention, it have good range and aoe.
Else, Marnox 296%x2 with 1s cd with a very wide attack range is the best general get-to-go summon.
Necroventer is 309% strike with 1s cd, and x2 if position correctly,
hence it is potentially the best single target hitter due to its narrow hitbox.
Some strong strike mobs like Harpeia/Cyclops/Unlocker/Mummyghast are pretty strong 1hit attacker, but easily lost to those 2 hits attacker.
Enchanter lightning hand have 20% matk debuff, so some magic attack summon may synergy well, but as I see there are very few summons with good magic type basic attack.
Chronomancer’s Quicken and critical attribute buff Summon a lot, so we also may test more chrono3sorc2 as it able reutilize some 3s slow physical attack summons. (but i don’t recommend to use R8 for old classes, there are more coming so we save for them, so instead of Sorc3 i think Sorc2-Necro1 or Sorc2-Chrono1 or Sorc2-RC is much better)