Why harpies don't use the exa bettle/rhinocebus combo? Harpie Lady sisters is lvl 6 and can be brought out from the deck with 6 cards that harpies currently use
Would you rather draw sisters than channeler? Would you rather special summon sisters rather than perfumer. If your answer is yes then you're free to use exa beetle my man.
If you play 2 sister you would be able to summon rank 6 with the same hand advantage as without, since you could search 2 with perfume using sister, you just need a right combo. That comes at the cost of 2 potential dead draw so not much people play them.
You would see some player like me occasionally play build with them thou if you are lucky.
There's a 60% chance of opening with any of those combinations, as reference the 30 cards neos that won a few tournaments (back when harpies were at the top) had around the same consistency.
Permune+egotist to rank 6 is a useless play, it's not better than just you straight up to making Cyber clash, but less consistent thanks to 2 big dead draw.
Don't forget Harpie cyber could be used more than, and help you draw 2 plus summon oracle for free. TTH isn't as essential as you think, you obviously only play Harpie as the standard deck from dlm.
As monster rhinocebus is miles better that cyber slash: it's quick effect too, pays the cost by itself and doesn't target
But in a harpie deck specifically? yeah cyber slash gives more to the deck. If rhino wasn't limited I'd consider use it in my extra deck but not as turn 1, now that it's limited I'd rather run any other limit 2 staple, thanks