This statement depends entirely on how you're evaluating the hand-buff value.
Ithlinne is 9 pts for 11 provisions. She only puts 5 pts on the board when she is played, however. You could say Sheldon is a 14 pt card for 8p with an Ithlinne buff (7 body, 7 damage) but then you're saying Ithlinne is a 5 pt card for 11p. For the math people, this ends up being 19 pts for 19p. It's the same idea with an Agitator. Sure, your Sheldon ends up as 10 pts for 8p (5 body, 5 damage). You would also be saying your Agitator was 2 pts for 4p. Again, the absolute value here is 12 pts for 12p.
One could also say the hand-buff pts belong to the hand-buff unit. So Ithlinne is a 9, Agitators are a 4 and Sheldon is 3 + damage. If you look at it this way Sheldon + Ithlinne puts him at a 10. One Agitator puts him at an 8. It's not so impressive.
Practically, it makes more sense to go with the first view. For the simple reason the value output at the time of the card play is probably more important. Even in that case Sheldon isn't as amazing as you've implied because you have to play low value cards to make him good. As an example, double Agitator, Ithlinne and Sirssa end up providing 15 pts for 27p to make Sheldon worth 26 pts for 8p. Yes, Sheldon is insane here. Those other cards, not so much. Even here it only works out to 41 total value for 35p.
I think you're misrepresenting the setup necessary to make Sheldon work. Needing to place 4-6 other cards in a deck to make a single card work is a condition. So is needing an opponent card at a certain value to avoid losing value. So is drawing several cards together. Even playing low value cards to make a different card more valuable is a condition. Conditions abounds....
Sheldon sees a lot of play because he fills a lot of voids in the ST faction. Nerfing a card over high play rates without considering context is a poor choice. Granted, it's probably what CDPR bases their nerf decisions upon. And reddit tears.... Explains a thing or two
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And, don't get me wrong.... I could see arguing for a redesign on Sheldon. A simple provision/value adjustment isn't going to solve much though. They rarely do.