Pet analyzes:
I made this section so anyone starting the game would have an easier choice on pet and what skills could be used as bosskillers. Note that between every difficulty your pets gain extra damage and health.
Lich King: (Spirit)
This is the most powerful pet in the game. At level 5 he gets Soul Blight skill, which lower enemy resistances greatly. Death Nova is a powerful synergy that reduces enemy health and leeches health for the Lich King. Wraith Shell makes the Lich King highly damage resistaned and almost impossible to kill. The last skill Arcane Blast is not needed for the Lich King to be the best pet of them all.
Core Dweller: (Earth)
The migthy Core Dweller is the second strongest pet. Strong on health, strength and the ability to provoke enemies to attack him and not you. The Inner Fire skill increases Core Dweller speed, health regeneration and dexterity. The Wild Fire skill gives to little output in damage and is almost useless. The Metamorphosis skill grants high health, damage absorbation and resistances and makes the Core Dweller the perfect tank. In legendary the Core Dweller is loose ground due to a more insignificant developement compared to his enemies though…Note that in legendary difficulty he is losing terrain due to his slow developement between difficulties, where pets like wolves gain real devastating power.
Wisp: (Storm)
The Wisp itself gives insignificant damage, but for characters dealing in elemental damage it has one of the best boosters in the game. The skill Eye Of The Storm grants 100% to elemental damage and high resistances to Cold and Lightning damage. A perfect pet for damage boosting.
Nightmare: (Dream)
Again as the Wisp, the nightmare is weak on damage. It gets abit more edge after level 5, but the reason to pick this oddlooking fellow is the synergies. Hypnotic Gaze spreads confusion amogst you enemies and works fine even with just 1 point in it. Mastermind is superb if you have other pets as it raises the damage and the regeneration of health and energy greatly to other pets. Without other pets the nightmare is more or less useless.
Wolves: (Nautre)
Wolves can be great or just suck big time. This depends on your character. At level 7 you get 2 wolves and at level 18 you get 3. The skill Maul is useless due to the extremely low damage output, but in IT expansion they gain % to reduction of enemy health from this skill. This skill should be maxed in legendary as it makes wolves one of the most powerful legendary pets. Survival instinct grants extra damage and damage absorbation when wolves go down to 15% of their health. Since wolves don’t deal much damage a % boost to damage is almost insignificant later in the game. I personally just 1 point this skill and recast wolves if they die. This works fine throughout the game. What you want from your wolves is the Strength of the pack skill (And Maul on Legendary). Strength of the pack boostes all allies psysical damage greatly and adds a bit to speed and armor. Superb skill but the pets them self are just boosting meatsheilds until Legendary where they weaken and totally rip your enemies apart. If playing melee with wolves they are great pets.
Sylvan Nymph: (Nature)
Weakest of all pets, but since she stays out of the harms way she has some survivability. All skills are abit below average and her synergies are fairly weak too. Owergroth gives a little defence and retaliation and Nature’s Wrath gives some elemental damage to her bow attacks. I useally put 1 point in her skills and stop there. If your playng Druid or Ritualist she will get some boosts from Nightmare and Wisp pet and get abit more usefull.
Construct analyzes:
Traps: (Rogue)
Traps are great. They work as nonbiological pets and do great damage. They also draws the attention of enemies which is very useful. Rapid Construction skill makes you able to create traps faster and cheaper and is a good skill if you rely much on your traps for defence/damage. Improved Firemechanism gives extra projectiles and adds to damage. All in All a great help playing rogue based characters.
Monster Lures: (Hunting)
Monster Lures are not that great. Best thing is that they are cheap and have the provoke ability. Traps do provoke aswell and are much much better, just more expensive. The Detonate skill is useless unless you playing an Avenger in which case Detonate is boosted by Earth Enchant Aura. If not the Monster Lure is a pretty weak alternative to Traps.
Timelimited summonings analyzes:
Outsider: (Spirit)
Now this guy is awesome. Dealing very high damage both psysical and elemental and having very much health. This is the best timelimited summoning in the game. Worth every one of the 16 skillpoints needed.
Ancestral Warrior: (Warfare)
With the Ancestral Horn skill you can summon 5 Ancestral Warriors. Their damage is not that great but you get 5 clowns running around and this makes the skill average for 16 skillpoints. All in all a good skill.
Bosskiller skill analyzes:
Collossus: (Defence)
Spend just 1 point and get 30% damage absorbation, 50% damage, 30% strength and 30 health. This skill is awesome just with 1 point. The skill does not get much better spending more than 1 point, so this is a great bosskiller skill and it’s only 1 point spend. This makes it the best bosskiller skill in the game.
Phantom Strike: (Dream)
Awesome Bosskiller and also a mob destroyer. With all 12 skillpoints it gives 190% to damage and your teleported directly into the attack. No damage taken getting close to your opponent. With the synergy Dream Stealer you get your mob attack and dealing 360 arc damage, 382 psysical damage, 405 energy leech over 4.0 seconds and 4.5 seconds stun to 6 targets at a time.
Lethal Strike: (Rogue)
This skill is evil. With all 12 points spend it gives 500% to psysical damage plus 390% to piercing damage. This totally rips your opponents apart. The synergy Mortal Wound is only for characters focused on bleeding/poison as it adds to % in thoose damage types. Considering how much psysical and pierce damage is deals this is not even needed. Maybe just 1 point in it for the 3 second stun to very hard bosses.
Study Prey: (Hunting)
The skill is a perfect bosskiller. Lowering both damage and pierce resistances on enemies by 50% imaging it with Lethal Strike. Double overkill beyond your imagining. The synergy Flush Out lower defensive ability and elemental resistances. The skill is not a must, but if dealing elemental damage or just having enough skillpoints in spare choose this synergy.