I've replied no to the poll. Before the poll I haven't even realized that sages are that important. While being efficient researchers, sages are not particularly good at other tasks. And in general research capability is somewhat overestimated. I often could research something nice, but I wouldn't have enough gems yet to benefit from it. For example, here's a bunch of my past games:
1) Jotunheim Iron Woods - no sages (didn't find them until very late, and then there was no point buying them). Instead I've found adepts of gold and iron order - that's nice for Jotuns - won. Key to success was early successful conquest.
2) Jotunheim Utgard - no sages (didn't find any). The only indies I've found were azure mages and shadow seers - about the last thing Utgard needs. Game crashed when I was one of the top contenders and in a good position to win. Key to success - diplomacy and finding Mount Chaining.
3) Pangaea default - no sages, until late (something like turn 50). I've bought some sages (because my research was still really low at that time), so they've been useful. I've passed that game to another person who has proceed to win (that other person was Norfleet though). Key to success - success in early wars resulting in a large empire plus diplomacy. Sages were somewhat helpful.
4) Caelum. Found sages, bought several (for random picks, rather than for research - I didn't have other indies with randoms). Won - the game was with very hard research and tough indies and that's very much to Caelum's advantage. Key to success - choice of nation
5) Caelum. Found sages (turn 20-25), bought very few of them for random picks, but few turns later I've found enchantress and stopped buying sages. Won. Key to success - successful early war, found enchantment+30 site, found Shamen and Druids early.
6) C'tis. Found sages early, bought plenty of them (around 2 dozens I think). The game crashed when I was in good position to win. Key to success - found crystal mages, sages and many good site in the early game.
7) Pangaea (default). No sages. The game crashed when I was in a good position for alliance win. Key to success - successful early conquest.
8) Pythium (default). No sages. Was top contender when the game stopped. Key to success - nation choice.
9) Machaka. No sages. Allied win. Key to success - early conquest.
10) Jotunheim Iron Woods. No sages. Win. Key to success - early conquest.
11) Pangaea (default). No sages. Win. Key to success - early conquest.
I've listed here the games I won or where I was in a good position to win when the game stopped (omitting those I've lost, where sometimes I had sages and sometimes I didn't, but the reason for the loss were various)
Only once sages has played really big role, in few other cases they only played a minor role. In half of the cases, I didn't use them.
The most important (though not necessary) key to success seems to be an early conquest. Doubling the size of your empire (including gold and gem income) really negates research benefits of sages, because you have twice the gold you can spend on mages. Finding some good sites (like Mount Chaining) can also turn the game. For many nations, finding indies with missing paths (like for Jotuns finding adepts of golden/iron orders) is much more beneficial than finding sages. So in my book, finding sages is a good event, but it's not the game decider. Starting position (which includes who are your neighbours) and finding great sites and indies fitting to your nation is more important.
Of course, my statistics come from a certain play style. I don't take drain scale, my usual magic scale is +1 to +3. I haven't played all nations equally and all my wins were with strong nations, sages or not, Ulm or TC is hard to win with.
Nevertheless, my point is that you can have strategy that won't crumble if you don't find sages and win with it.