4s

You would be surprised. I tend to get my archers killed faster than my wisps. Also, remember that detonated wisps give no experience to the Blademaster. If the bm is underleveled, he is basically useless for the rest of the game. You may take a hit early but shouldn't lose more than 2 wisps. The key here is getting to T2 as early as possible. Once you have a KotG, the effectiveness of the bm drops to almost zero.

Ok, let's go over the night elf units

Archers: Powerful offense, terrible defense. If you can keep them from getting targeted you can kill almost anything. Straight archers has been a 4s strat for a long time but fell out of practice once Blademasters got their buffs. You can mass them, but by the time you have 40 food you should probably be at a point to get better units.

Huntresses: Decent melee unit with bouncing attack. The problem here is unarmored defense type. Anyone who knows what they are doing will focus fire them with ranged. They have a lot of hp, but go down far too easily once targeted. Best if used in combination with partners getting ranged because they are affected by Trueshot Aura. They are particularly effective against footmen, riflemen, and archers, but not as effective as they should be against spiders because of unholy aura.

Dryads: Spell immune with slow poison and a dispel. Can be massed very effectively. They HAVE to be micromanaged heavily. They will attack garbage units instead of the heavy air that are the main threats in most games. Abolish magic needs to be researched ASAP as it is only 50 gold and makes skeletons useless for the rest of the game. Abolish Magic is a decent move, but autocast doesn't damage summons. You have to manually cast it to take out summoned units. With a few though, skeletons, scarab beetles, and water elementals should die the instant you see and target them with the spell. Primary use of dryads is taking down air and slowing heroes. Even Death Knights with Unholy Aura won't escape slow poison. Be careful of mortar teams. If you see them, get away. You are much more mobile than they are.

Bears: The unit is completely useless until you have master training. They have no hp and give a lot of experience to the other side when killed. Picking one up for roar is ok, but it really isn't a good unit to mass in 4s. Leave the melee work to orcs. If you do decide to mass, then you will need to get into the other sides ranged units because you won't survive 1v1 against human or orc melee. Because of their size, they aren't very mobile. Rejuvenation is nice for heroes, but if you are casting it, you aren't in bear form and are a free experience tome waiting to happen for the other side.

Mountain Giants: Wait...really? Don't get these. Ever. They are the very definition of a tanking unit. They have a ton of hp, an armor type that makes them hard to mow down with heavy air, and a taunt. The problem is they can be ignored. The taunt is weak, the food cost is too high, they are too slow, and if you get them you aren't getting something better. 1 dead Mountain Giant is enough to level up almost every hero on the other side.

Hippogryphs (unmounted): A high damage air attacker that can mow down air units pretty fast. The problem is their damage is misleading. Because every air unit but copters is either light or unarmored, the normal damage doesn't get a boost. In addition, by the nature of them grouping up, they are very weak against slowing (frost nova or frost wyrms). Really the only time to mass them is against wyverns, gryphons, or dragonhawks. They also have the problem that they get webbed very easily and if they are webbed they can't attack, and almost every game will have at least 1 person with spiders.

Hippogryphs (unmounted): Poor air unit but with the ability to switch back to the archer/hippo on a timer. Don't intentionally get them because of their low damage, but if you need to counter something (Wyverns especially) they have uses. Same as the archer, they are sniper units. If they get targeted they will die. They are weak against slowing and terrible once webbed.

Druids of the Talon: Requires a lot of micromanagement. Weak air unit but with the ability to massively lower armor of almost anything (including even heroes and tanks). Basically you need to tech to T3 fast because the upgrade to let them cast faerie fire in air form is essential to using them correctly. It's pretty simple. Go into battle, cyclone everything you see, and jump back into bird form and take out any dangerous air (particularly frost wyrms). Have a few pop back to caster form every so often and re-cyclone things.

Faerie Dragons: Weak air unit with a mana burning ability. Don't mass them, but especially when the other side has casters, pick up 4-5 and drop them into the middle of the opposing army and use mana flare. It affects any caster units (including heroes) and have very high armor. As attacking units, faeries are terrible with their low hp, low damage, and disappearing the first time they get hit. They should be used strictly for the mana flare ability and can be used in combination with chims/hippos/DoTTs.

Chimeras: High damage, heavy air unit. They hit hard...really hard. A mistake a lot of undead players make is trying to go 1v1 against chims because of web. The chims will destroy the spiders because of the splash attack of the chims. Corrosive breath is great for hallsmashing, but comes with the drawback that killing orc/human towers is now going to be a pain due to the armor type. If you see a human city towered heavily, don't tech corrosive breath. Magic will do extra damage to the heavy armor of the towers and it does more base damage anyway. Once you get 6-7 chims you can think about hallsmashing (9+3 heroes is ideal). Basically the idea here is you can take down halls before the other side can be coordinated enough to town portal in. Since there is a delay from when the town portal scroll goes off and when it is cast take advantage of it. You know the other side will be slow, and you can start your cast out of the city at 20-30%.