Teams like Castres, Racing and Montpellier are like the Ospreys and Glasgow of the PRO12. They only do well because they only realistically can win domestically and because best teams wear themselves out in the final stages of the European cup. As many players of have said it's the closest thing to international rugby.
I don't believe that a second, although it's yet another one of those modern "urban myths" in the Top 14 that's been circulating well these past 2 years.
Teams don't "wear out" that badly that it makes a decisive difference, Toulon, Clermont.. those are high profile clubs with enormous depth and a brilliant rotation system. Whether Castres took Toulon by *surprise* in 2013, probably, although the latter were warned this Castres side was no joke since they'd made it all the way there to the final.
Again, that same Castres side gave Toulon one hell of a run for their money in last year's final and the best fight any team has given Toulon (Munster, Leinster, Saracens...etc...) in any elimination game. It's that same Castres side that went to Clermont in the 1/4F to put the 76-game win streak to sleep forever.
It's that same Castres side that beat the crap out of Paris, beat Toulon, Racing Metro, Toulouse, and tied with Clermont during the regular season. Castres was no joke the last two seasons.
The simple fact of the matter is those clubs don't have the depth for both fronts and the Top 14 has the most strain over its actors than any league in the world, by quite a distance I'd project. What they manage in the Top 14 is LAUDABLE enough, given their tiny budget in comparison to the Clermont, Toulouse or Toulon. They send out their 2nd, even 3rd stringers along with good players to see if they can manage an interesting result, but you've got to question the commitment in most of those, especially when they've lost on opening weekend as they always do, and I see names on that sheet I literally *never* do during the regular Top 14 season, i.e.
what actually counts for them.
So, nope. It's not like you put it. As for Montpellier it's a disaster overall not just Euro level right now. They've like a 4-game losing streak domestically. Their coach, the hopeful joyous young Fabien Galthié, has apparently resigned. They're in a full-scale crisis, just like Racing last year. But both most definitely can "compete". In fact watch Racing this season, Montypellier will have to wait a little longer.
