the power balance after that wind guy vs rock titan actually reminded me of One Punch Man in its world lore and general state, only hero-monster war is not public, and 5 "S-tier heroes" are actually founders, not "employees" . So while some of them might genuinely work tirelessly to defend general populace(like that friendly fire(?) dude you meet at the mess hall), others might have their own agendas or busy with their own stuff(eg, Metal Knight or Blast from OPM) , and overall they are not taking orders from anyone. Doctor guy might have some leverage though, as they seem to listen to him, but that power dynamic is yet to be explained.
As regards to the Valravn fight, besides someone already pointing out that he tends to flee from stronger opponents, I think the main point of this fight was to test the newbie and to also gain some more rep for MC and by extension HERO . In worst case, MC would make a nice bait at least(it's not like can use 5-tier powers in the middle of the city, so keeping him distracted and in one place was necessary for some precision work).
Besides, you don't see likes of Steve Bezos or Bill Gates going around doing tech support or deliveries. If Valravn is considered small fry, they might only feel the need to step in only when all the down-the-ladder options fail. It does leave me wondering on the power level of monsters that can give pause to those 5, however, and how they managed to keep those fights secret. Perhaps, it's just through sheer numbers that they are kept busy, or maybe the warp/tp real tough opponents far enough that those fights wouldn't be noticed(like to the moon, or deep under ocean)