Outside of what is posted in the primer about it I don't know what else i could add that would dissuade you. Quote from primer: "Living Wish: Decreases consistency of drawing into the combo naturally (which is ideal) and slows down the deck. Also makes you more susceptible to counterspells."
Additionally, you can run a search through the entire thread for posts that talk about living wish by searching "living wish".
Here are the statistics
Assumptions: the "combo" is dark depths + hexmage OR stage; the "tutors" are 4x crop rotation and 4x sylvan scrying; stats do not take into account Brainstorm or Sylvan library or sensei's divining top.
Without living wish
Chances of drawing the combo naturally within the opening hand - 26.11%
Chances of drawing the combo naturally after drawing 9 cards (3rd turn if you are on the play turn 2 on the draw) - 36.62%
Chances of drawing both combo pieces or a tutor to get the missing combo piece in opening hand - 72.90%
Chances of drawing both combo pieces or a tutor to get the missing combo piece after drawing 9 cards (3rd turn if you are on the play turn 2 on the draw) - 84.40%
With living wish (-1 depths, -1 stage, -1 hexmage, +4 living wish)
Chances of drawing the combo naturally within the opening hand - 17.08%
Chances of drawing the combo naturally after drawing 9 cards (3rd turn if you are on the play turn 2 on the draw) - 25.06%
Chances of drawing both combo pieces or a tutor to get the missing combo piece in opening hand - 76.73%
Chances of drawing both combo pieces or a tutor to get the missing combo piece after drawing 9 cards (3rd turn if you are on the play turn 2 on the draw) - 87.32%
Braintstorm vs 4 other Tutors
Chances of drawing both combo pieces or a tutor to get the missing combo piece after drawing 9 cards (3rd turn if you are on the play turn 2 on the draw) - 88.07 (+4x brainstorm)
Chances of drawing both combo pieces or a tutor to get the missing combo piece after drawing 9 cards (3rd turn if you are on the play turn 2 on the draw) - 93.44 (+4x Tutors)
Takeaways from statistics
1. you reduce your chances of drawing the combo naturally by 10%
2. Adding 1 additional tutor ONLY increases the chances of getting the combo by 3-4%. This number is certain to be subject to diminishing returns.
3. You have 5.37% better chance of getting the combo with 4x tutors than with 4x brainstorm. HOWEVER, this does not take into account the added value of brainstorm being able to find other cards, like sideboard pieces, OR its ability to put back multiples of a card you don't need.
4. You have a 12.04% better chance to draw the combo pieces or tutors after drawing 9 cards with 4x tutors instead of 4x brainstorm.
Non statistics stuff
You can also think about this logically. Why do you lose most games?
1. Were you killed because you couldn't find the combo in about 4 turns?
2. Were you killed because a combo deck beat you first?
3. Were you killed because you couldn't attack with the token (i.e. it was STP / karakas / terminus / maze / etc)
4. Were you killed because you were out tempo'd?
I think the general consensus is that MOST games are lost because of #2 & #3. If you are losing because of #1 then i would first start by looking at the hands that you are keeping.
BUT for the sake of argument lets consider how living wish helps vs each of the options.
1. It cost 2 mana so it is like 5-8 sylvan scrying. Some lists don't run sylvan scrying because expedition map is better for their manabase. I don't think many versions of the deck run more than 8 tutor spells. You could consider Negator's list to have more if you considered the brainstorms but other lists that don't run brainstorm often use sylvan library. Drawing into the combo naturally happens fairly often.
2. If you are losing before turn 3 living wish won't help because you won't be able to cast your wish target until turn 3.
3. One of the best cards you could get with wish to combat these issues is Not of this world and you can't get that. The second would probably be pithing needle. The only two targets i could find useful are sylvan safekpeer, and wasteland / ghost quarter.
4. If you are getting out tempo'd then you surely won't have extra time to cast a spell.
ALSO, please let me know if the statistics were helpful or if you would like me to run other statistics.