[Closed] NL10 : Set overprotected ?

no it´s okay. you made a potsize raise (=3 x betsize + pot).
There is no real differenz, if you raise to 3,5$ or to 4$. He would fold in both cases.

If so, then why the Call15 rule. The board is very often 2-suited and even if I get the 10 % luck to hit a set, I usually chase them out of the pot because of protection or because they just don't hit anything.
I almost never get to win 10 times the price of the call preflop. I usually have to bluff them out to get anything.

I think call 15 is good enough to make it profitable. You hit your set about 1 in 8 times, and you double up once in a while too.. Don't mind scaring out villains once in a while.. having them outdraw you and stack you off is worse (or just getting stacked off anyway):

Known players: (for a description of vp$ip, pfr, ats, folded bb, af, wts, wsd or hands click here)    
[tg]Position_Stack:hands/vp$ip/pfr/af/wts/ats/foldbb/w$sd;MP2$2,53:///////;BU$6,89:///////;Hero$4,88:///////;BB$2,82:///////;[/tg]
0,02/0,04 No-Limit Hold'em (8 handed)
Hand recorder used for this poker hand: Texas Grabem 1.8 by www.pokerstrategy.cc.

Preflop: Hero is CO with 4♣, 4♦
2 folds, MP2 calls $0,04, MP3 folds, Hero calls $0,04, BU calls $0,04, SB folds, BB checks.

Flop: ($0,18) A♠, 4♥, 9♥ (4 players)
BB checks, MP2 bets $0,18, Hero raises to $0,50, BU calls $0,50, BB folds, MP2 calls $0,32.

Turn: ($1,68) 8♦ (3 players)
MP2 checks, Hero bets $1,24, BU raises to $6,35 (All-In), MP2 folds, Hero raises to $4,34 (All-In).

River: ($12,37) 8♥

Final Pot: $12,37

Results follow (highlight to see):
BU shows [ 9c, 9d ] a full house, Nines full of Eights
Hero shows [ 4c, 4d ] a full house, Fours full of Eights
BU wins $2.01 USD with a full house, Nines full of Eights.
BU wins $9.85 USD with a full house, Nines full of Eights.

I think it's dangerous. I had blank sets due to oversets before as well.
And while I wasn't outdrawn yet, by scaring drawers out, I stacked many people holding a set with a flush or straight myself.

I think in nl, you want people to call expensive draws. With that sort of raising no reasonable player will call you without a great hand or a hand that beats yours. The raise was fine, but sometimes you need to raise amounts that make draws unprofitable but are still callable by bad players.