I did not say anything about carrying and what I said was the “worst-case scenario”, the SSF journey (that I also do in this season).
The general idea is to look at the skill tree, select what skill you want to use as your main skill, check how many synergies and bonus skill it has (like elemental masteries for the Sorc), so you will know that when maxing them how many point will have on a given level.
Another important idea is to only add points to a main skill when you feel that it is underperforming. This is to see how effective it truly is with your playstyle. While main skill are technically always maxed, this is still a good way to forecast its effectiveness for later harder gameplay.
You asked hydra + (orb or blizz). On Normal you can start Blizz (its available at lvl24, so it is reasonable to start testing with it). Add just 1 point to it. At lvl 24 you probably wont have +skills, maybe 1 or 2 if you are lucky, but that is not a game changer right now. Assign this skill to the button you like and go, see if you can kill mobs with it. If even with 1 pt is seems strong, that is a good indication that it will stay strong later. If not, then check how many synergies it has. Hydra has many, so for me it is a red flag that PROBABLY it will only be super effective when all synergies are maxed and for Hydra it means 60 + 20 pts (20 Hydra, 20-20 Fbolt/Fball, 20 FMastery). This leaves very few points on other skills (not to forget you need Teleport and I tend to add 1 on Warmth, that are immediately 3 points that you cannot use for main skills), so for me this is another red flag that it is either not good for non-endgame builds as main skill, or it will only shine in particular areas, but generally speaking I would not rely on it for playthrough. You can still play around with it and see how effective it is FOR YOU. “FOR YOU” is the most important thing here, because we all play differently and what works for a speedrunner/streamer, might not work for you.
If you are satisified with Blizz/Hydra or Hydra/Blizz, then good, you found a working build for yourself! I would personally level up as much as I can to save respec for Hell, unless I am truly stuck.
When you reach Hell, that is when you need to be a bit patient and start testing in Act1, but generally speaking this is when you can use your first respec and do a similar testing with FOrb. Just go and start killing around and you will see how good that skill is for the amount of skill points you spend on it. Once again, dont max out the skill just yet, but gradually go up until you find it effective.
If you are patient you should still have at least one, but rather 2 respecs, so you can still change which build you feel as “yours”. Just because you have 10 unspent skill points, it does not mean you need to spend them. Patience and only spend pts when you truly need them. Most of my char at Hell has 30-50 stat pts and tend to have a few skill points as well when I am testing a new build.
But this is my 2 cents, you dont need to agree. Many players want instant results and they dont like finding out things on their own. I am probably too old for this and I enjoy the path that leads to undeerstanding a class in D2. 
