i think its a myth that you should ignore energy, or some nonsense spread by people who only play certain classes and should not speak for all, the same way that only act 2 merc is viable. you are going to love rogue if you give her a chance, especially the fire one - huge shoot range, and lightning wolf is a good buddy against crowds of weaklings if you plan to be a one on one kinda guy. barb merc can seem much weaker than act 2 merc, he kind of is. but thats only because like much, much later, he suddenly matures and starts using his skills nearly all the time, stunning and bashing left and right. he has a good offensive potential. it kind of works the same for rogue, though more gradually. she will start firing more rapidly as her level progresses. cold wolf speaks for himself, very good defensive choice for melee players. and fire wolf… well, he is bugged. there is no way around that. but if you play as ranged, you can largely ignore this bug as he will stick with fire balls, blasting up everything trying to close in with somewhat efficiency. i mean, it is aoe, what more can you ask? everybody loves a little aoe damage. and it would be bad if they performed anywhere equal to sorceress. keep those guys around if any of your characters struggle clearing out crowds. if you ever use them online, or since you use plugy and probably have ladder runewords activated, give them tal-thul-ort-amn runewords on swords and shields to really boost their damage potential and fire rate. remember only to hire a new merc in normal difficulty, they are bugged in other difficulties and have worse stats.
all ranged mercs have the plus that they dont die as often, even during boss fights,
so they wont bleed your gold and you will have more to gamble with. yay!
or if your happen to get a huge bill each time from repairing equipment, yay…
here is what i have to say about energy. the one time where you can ignore energy is if you are certain you only require a little leech to sustain yourself. for someone like barbarian, most of his skills cost no more than 2 mana so it makes sense for him. for others its very expensive to perform their main offensive skills. when you play ranged, you have even more reason to invest in energy, because you wont get hit that often, and killing enemies before they reach you is better than worrying about whether they get to reach you and take a chunk out of you, but you also make that worry more relevant when you run out of mana often
another good reason to invest something in energy is it makes mana potions have a greater chance to apply double effect, the same way it works for vitality. this is also something to keep in mind if you are a warrior class (amazon) and your skills are expensive, because warriors gain less from mana potions than mages do and will need that extra mana gain during combat. though you should keep in mind that your mana gain from energy itself is also less as a warrior class than it would be for mages, so pouring too much into it is not that advisable. then again, mages skill costs can be mad (some necro golems at level 20 cost nearly 200 mana to spawn), warriors not so much even on their worst, the gain should be noticable even if its much smaller
if i dont play as a class with skills that can sustain themselves, my rule of thumb is to get energy up on 50. if my skills still drain my mana too fast at that point, i go somewhere at 70-80, and finally up to 100 if i feel relatively secure about doing that, like playing a summonancer. for your freeze amazon, i dont think it would hurt you getting up to 70-80 energy if you can manage. having a little less vitality wont hurt if you can freeze crowds more consistently. also good for fire amazons to keep the enemies locked in hit recovery
i always keep in mind that my mana continues raising on each level too, especially on a mage character, so this is something to remember in the beginning of the game. you will always run out of mana there with expensive skills and thats okay. you can pay attention to how much mana your class raises each level, and pay attention if your skill raises in mana cost too, and sum it up in your head, how often can you use this skill before running out of mana later? will you likely run out of mana faster than life during bossfights? can this also cause too many breaks back to town while clearing areas?
this is of course while you create a new character, i know this is not relevant to you right now. but its good to remember for next time
i also would not recommend relying on getting a huge mana pool through equipment. when you really think about it, its a waste of attributes on those items. i would rather spend a few points in energy instead of pouring it all into vitality, than suffer from having to wear some unique item with huge mana increase, but does little else, or keep some charm doing the same out of desperation, or having to look for enough mana per kill or leech to make it turn positive. i think your character will suffer a lot more from doing that, also like you experienced it, than the cost is putting some points into energy. so dont worry about it, whatever keeps your character lethal.
it will most likely make them avoid more deaths than contributing to it if anything. this is also coming from someone who plays nothing but hardcore. i approve of its safety and usefulness