just for a bit clarification:
Decoy and big bosses: Some big bosses (by "big" i don't just refer to 5 prime evils) do attack decoy. A very good example is Izual: decoy is his favoriate - you could have a lvl ~15 act2 merc kill Norm Izual in a big game, if you have a relatively durable decoy. But Baal and ancients will completely ignore your decoy. I've never seen Diablo (nor his clone) attack decoy, though this might be because decoy lasts only a nominal time in the area effect of Diablo's attacks. (in 1.09 my strafer would at least try to cast decoy to gain 1 extra attack even against big D).
Norm/NM games: a typical javazon build has no real problem in Norm, NM, and up to Hell act1: she can survive virtually everywhere even with junk gear. She typically enters Hell at ~75. Starting with a few places in Hell act1, such as Mausoleum in the Burial Ground, her killing power will significantly decrease compared to what she had in NM, unless you significantly improve her gear to counter that. That's where the real challenge to a javazon starts.
Hell viability:
if she solo and tries to do all quests in Hell, unless she's fully twinked with very decent gear and also you are a very, very experienced player, Hell act2/3 will give her big headaches in almost every place. I'm not saying she can't solo through entire act2/3 without dying even once. I'm just saying it'll be significantly more difficult - especially on HCL.
Theorectically, you could resort to melee or switch to bow to handle LI, but in face of thousands of LI's in Hell act2/3, I would prayer that you would have that type of patience to stay alive while killing them 1 by 1. Not to mention some of the LI monsters are immune to physical, some may have very dangerous mods, and some may be protected by other very dangerous bosses.
A few examples: unless you are 120% ready in terms of gear, you'll have a great chance to die if your valk, merc and yourself attack huge boss packs of beetles and other monsters all at the same time, if you enter a tomb in act2 and get surrounded with a huge mob and refuse to exit the game, if you jab a boss pack of black souls in act3, if you enter the ruined temple and refuse to exit the game immediately, if you attack stygian dolls in melee or if they catch you and you choose to open fire in melee, if you try to jab the witch doctor in the Flayer Jungle.... If a coucil member boss is spawned with PI + LI, you may find it would take you years to finish him off, assuming you are a *PURE* L-based javazon, though he should be only able to kill your merc.
Hell act5: with numerous "guest" monsters, it has all the dangers you have had in act2/3, and much more!
Act bosses:
Hell Andariel is not a real threat to any questing HC amazon past about ~75. Hell Duriel is hardly able to kill a high-lvl Valk (or even just to hurt her), so it's a matter of time for you to kill him. Hell Meph himself is not dangerous even if you get hit by his most dangerous attacks, assuming you use a shield full-time. But similar to Hell Baal and Hell Diablo, if your pure L-based javazon wants to kill him without using Charged Strike, be ready to enjoy a prolonged fight. For practical reasons, Hell Diablo, Hell Baal, and Hell ancients are not killable to your pure L-based javazon if she chooses to use only jab or throw skills - it would take just too much time, even if you can.
My own xp:
When the first HCL came out in 2003, I built a pure L-based javazon and was determined to at least try to solo Hell with her, but unfortunately, she got PK'ed in a public game around lvl 70. Later, I tried but have never got enough patience to actually solo through entire act2/3 in Hell. My pure L-based trapsin did that, however, on the first HCL - and she was untwinked, and solo'ed entire Hell except for Hell ancients. Unlike a trapsin, an untwinked Javazon has virtually no chance to survive act2-5 in Hell solo, unless she's lucky enough to twink herself using what she has found in NM and some places in Hell act1 - in other words, compared to a trapsin, she needs much better gear to be able to defeat Hell.
BTW, critical strike and charged strike are different (I guess I have made a clear distinction in my posts). Critical S. is unimportant to an L-based javazon: it only slightly affects her ability to leech. since she typically has already got a decent % ed from her wpn or gear, the occasional doubled base dmg can only be transalted into a small % ed on average - not worth even 1 extra skill point in this skill. If you really want it, try to increase %Deadly Strike from your gear (note: deadly strike and critical strike do not stack up, so it's an either-or deal here). If you need to boost your prowess in physical melee attack, the best and the right way is to increase your %crushing blow up to 100%. Against big bosses like Hell Baal, this can be translated into (literally) 10000% ED on your melee javelin in an 8ppl game. Open wound and prevent monster heal can also help a lot.
Charged Strike is a melee-boosting skill. Against a single big (the bigger the better) target, it's a killer skill even in 8ppl Hell games. It's a must-have skill to a PURE L-based javazon. LF is a synergy for this skill.