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Tyres

I have never used the hards at all in a race, their pace when I try them in practice is prohibative. I do however think the difference between tyres can be frustrating. I was out raced recently by a guy running mediums, when i had fresh supersofts for
A splash n dash over the last 5 laps. That said its all about learing and experimenting. I've gone for a risky ss blitz in my next race given the massive speed diff, and to try bag pole. For much of the last few season I've played safe and gone medium. But nothing ventured nothing gained. I feel.comfortable now that i've won so time to experiment

Imo tyres are fine because winter(ss season) will be coming soon. I have won a few races doing 1 stop hard strats in 50% races. But almost any start can work if you have a fast enough car...

Hards are only slightly over powered in the summer
I have won almost 10 races in a row by using hards in my 100% race strats; I am in an active league where everyone else tries softs at least once.
But I have not dominated races just from using the hards.
It is close enough now imo and this time of the year should be the best for a mixture of strats.
So far Australia, Europe, Monaco and Singapore are the only tracks I know where hards are sh**.

I think that @Lancia has some reason, in my league cars with hard tyres (in Germany at 14°) appeared to be way faster than soft... A strategy with 20-20-20 H appeared better than any strategy with soft (look at first stint of Daoud).
Saturday 100 - Germany

Yeah when the temps are not so high, you'll get to see some crazy variety of strategy.

For 50% distance, take a look at International GP Championship's Elite tier for instance, the best daily 50% distance league atm. Belgium had different teams trying so many different things. ss-s-s, ss-ss-h, s-h, ss-h (which won!), and so on. And all those strats finished within 5.5s of each other! And it's not the only race where you can see tons of variety of strategy and results which are so close. Another great 50% league with lots of diff strats is iGP Champions' Elite tier (1 car league, so 32 teams per tier). And I'm sure you can find other top leagues with managers using a good variety of strats that are competitive.

It's not just getting the right strategy for the temps and track, but also executing it well (push levels, management of tyre temps and tyre wear, fuel, KERS usage, etc.). Competing in that league with my highest leveled team has really opened my eyes to all the possibilities available. And it just goes to show how crazily strong Joey McLane was, dominating these top leagues for multiple seasons before he retired...

Hungary and Germany are some examples where Hards work well in certain conditions and not in others. For 100%, I just did Hungary with this team at 14C. I put on Hards for one stint, and it was impossible to keep temps above the blue without going push 4 and 5 all the time and burning so much fuel and engine wear, and I was getting rampaged by the SS and S runners. At 30C, however, a 3 stop stint in 100% for Hungary may be one of the ideal strats. Similar to Germany, where Softs & Supersofts and more stops work better in lower temps, but Hards and less stops may be able to compete in higher temps.

So study some strats, experiment a little, and you'll definitely get a much better idea of how tyres work in this game!

@Leo: Hards can actually work very well in Europe and Singapore since they tend to have higher temps. For instance, the top managers in iGP Champions' (50% league) Elite tier put Hards to very good use in Europe (winner this season is 2 stop ss-ss-h), and 1 stop is seemingly the standard strat there, as oppossed to 3 stops ss in most other competitive 50% leagues.