Humans joined the galactic community after discovering a Prothean data cache on Mars in 2148. Their devotion to understanding and adapting to modern warfare left the staid Council races stunned. Humanity's persistence and unflappable spirit has taken them further than anyone in the galaxy could have imagined.
Master of nothing but proficient in everything, human sentinels are often relied upon to draw fire on the battlefield. Sentinels relish their opponents' look of surprise when they realize they were focusing on the wrong enemy all along.
It may seem illogical, but power damage increases do not affect the strength of biotic explosions: the strength of the combo is determined only by the total of the ranks of the set-up and detonation powers used and any rank evolutions taken which specifically increase the damage of biotic combos. As a result, Tech Armor, active or not, cannot increase biotic combo damage, and neither can Alliance Training passive bonuses. It does however increase damage of powers and so it will help deal more damage, but will not effect the damage of Biotic Explosions. That being said, you can run around abusing the explosive Tech Armor to stagger enemies that get too close, explode it to fire off biotic combos faster, and reactivate it to take enemies on in longer-range combat.
Because Human Sentinels are power intensive, a light loadout is recommended. Consider a Carnifex or Disciple, or both.
On higher difficulties, all enemies with dodging capabilities dodge with increased frequency, making set-up and detonation a pain. Either shoot first to cause the enemy to dodge or get close enough to make the thrown power unavoidable. Another option is to team up with an ally who has a "hit-scan" power such as Reave--once a target has been primed, a biotic explosion is only 1-2 seconds away since the recharge speed of Throw tends to be faster than the frequency of an enemy's dodge.
Because of power bonuses from both Tech Armor and Alliance Training, using Throw on the Human Sentinel is exceptionally powerful. One shot from a pistol, like a Carnifex, followed by a Throw, will quickly and efficiently eliminate any unprotected enemy.
Although the Human Sentinel doesn't have the baseline physical durability of the other Sentinel classes, it makes up for this by still being able to dodge and roll away from attacks. With up to a 50% damage reduction to handle weaker attacks, and the speed to get out of the way of heavy attacks and execution moves, a well-played Human Sentinel is more than capable of surviving almost any firefight.
Biotic explosions are deadly against Atlases, especially once their shielding has been removed.
While Phantoms can be detonated, their gauntlet can block powers, preventing explosions or damage. Counterintuitively, one can simply spam powers without specifically aiming for a combo to try to pin them down for weapons fire.
Alternatively, one can goad the Phantom into performing acrobatic flips by using rapid weapon fire. Because a power launched at a Phantom in the middle of a flip will track her normally, this is an effective strategy if the Phantom is a good distance away.
Guardians can also be detonated, but only when hitting the Guardians' bodies. Throw can be used to stagger them, exposing their bodies to gunfire. Another tactic is to send Throw at their backs--usually the power and physics damage will kill them outright. If not, they'll have dropped their shields for easy pickings.
Since most enemies have either just health or armor, biotic combos are devastating against Reapers, although a little time-consuming. Make sure you have a good means of defending yourself at close-quarters or medium-range while your powers recharge.
Throw will do a good job suppressing Husks, Cannibals, and any unshielded Marauders.
Human Sentinels do not excel against the geth, as they have no powers that strip shields. This can be somewhat remedied by carrying an anti-shield weapon such as the Acolyte.
Human Sentinels do well against geth with allies that have tech powers such as Overload and Energy Drain--Throw, with its low cool down can help set-off quick Tech Bursts. This can also be accomplished by yourself by equipping Disruptor Rounds--shoot, then Throw.
Warp can be useful against the Geth Primes and Geth Pyros, but against anything else, you should consider using your weapons instead.
The Geth Hunter, of all the geth units, will most likely give you the most trouble. Without auto-target and the trajectory-tracking function of projectile powers, such as Warp and Throw, hitting cloaked Hunters can prove difficult, especially if you don't realize they're there, and even more so if they see it coming and dodge.
Bombers will cause no end of trouble to your team and should be dealt with quickly. They are however, quite fragile, and you will be protected by Tech Armor, which will give some protection, but is not absolute against the many cluster grenades they will drop.
The Human Sentinel will work well here, with Warp being able to affect every single enemy in one form or another. Enemies will either be softened up due to the armor weakening, weakened by DoT, or their barriers will be heavily damaged. It can be used with throw to detonate explosions which will cause no end of trouble for the Collectors.
Throw is very useful against Abominations, since they explode upon death if you do not melee them, or hit them in the head with a gun. This power will give you and your team some breathing space to kill one or many Abominations and prevent their explosions from doing extreme damage, especially if said foe is possessed.