I agree that statement 2) alone, is sufficient. However, for reasons which (as far as I've noticed) have been overlooked, statement 1) should also be sufficient:
Consider that simply by the givens of the problem, we can narrow down possible values of p, which is necessarily a positive integer. Since 11p players play tennis, we know that 11p is less than or equal to 60. We immediately know that p is a natural number no greater than 5.
Now, we can also build upon our work with statement 2). Supposing we use the following labels, based on the work of flyingbunny:
suppose there are:
s: players only play soccer
t: only tennis
g: only golf
x: only play soccer and golf
y: only play soccer and tennis
z: only play tennis and golf
p: play all the three.
we can have:
a) s+t+g+x+y+z+p+2p=60 ==> s+t+g+x+y+z=60-3p ==>> a1) 2*(s+t+g)+2*(x+y+z)=120-6p
b) s+x+y+p=6p
c) t+y+z+p=11p
d) g+x+z+p=8p
from b) c) d), we have
bcd) s+t+g+2*(x+y+z)=22p
From this work, we can double the bcd) and arrive at 2s+2t+2g+4*(x+y+z)=44p. We can subtract the a1) equation from this, to get 2*(x+y+z)=44p-(120-6p)=50p-120, which simplifies to a2) x+y+z=25p-60.
However, statement 1) tells us that half the players who only play soccer and golf but not tennis is half the number of players who play any other combination of two sports. In other words x=(1/2)*(z+y), or 2x=y+z. Plugging this into a2) gives us 3x=25p-60. From the beginning, we narrowed p down to 5 options, (1, 2, 3, 4, or 5). We can immediately eliminate 1 and 2 as solutions for p. Note also, that 4 and 5 are not possible solutions for p, since 125-60 and 100-60 are both not divisible by 3. In fact, the only solution for p is 3. Essentially statement 1) implies statement 2), and is therefore, also sufficient by itself.
The fact which I believe was overlooked is that when we are told that one group is half the sum of the other two groups, we can deduce that the sum of all 3 groups is of a size divisible by 3. This, coupled with basic eliminations regarding possible solutions for p, limits our solution to one possible answer.
Please comment if there is something I have missed, or erroneously concluded. I'd like to see this post addressed, whether or not I am correct.