Instead of telling you whether or not I think a sector is overvalued, which, to be honest, I don't know (no one knows), let me talk to you about strategy.
If you like the biotech sector but think that it could still have some room to fall (timing uncertainty), consider putting on your position using laddered puts. So, if you wanted to put on 4 tranches, you may purchase 1 tranche today and also sell the equivalent of 1 tranche of puts at one strike, then go out to next month and sell another tranche at the same delta strike, then go out another month and sell the third tranche at the same delta strike.
This way, if you are right and you have picked the bottom in the biotech sector, you get to reduce your cost basis by collecting money on the now junky puts. However, if you are wrong and the biotech sector continues to fall, the sold put continues to force you to exercise at the lower price (assuming you take assignment). Of course this all assumes that you like the biotech sector and want to start building a position today.