Krogan are large bipeds native to the planet Tuchanka, a world known for its harsh environment, scarce resources, and vicious predators. Until the invention of gunpowder, the leading cause of krogan fatalities was "eaten by predators." Afterwards, it was "death by gunshot". Though slow, krogan can take tremendous damage in combat, allowing them to inflict grievous harm with impunity.
Armored like a tank--and as slow as one--an angry krogan has more going for it than the species' infamous belligerence. It should come as no surprise that a krogan dishes out as much punishment as they're able to take on the battlefield.
Krogan Charge - The Krogan Battlemaster Vanguard charges forward a short distance and strikes an enemy with held weapons.
Krogan Battlemaster Vanguards lack a dodge maneuver.
The Krogan Battlemaster's Biotic Charge is quite different from other Vanguards'. Charge takes longer to reach its target and has a longer cooldown, but deals more damage.
The Krogan Battlemaster has 250 more points of health than either the Krogan Soldier or the Krogan Sentinel, as well being able to have 1800 shields if Fitness is leveled towards this. With the ability to restore shields in an instant with Charge, and with Barrier evolutions that decrease damage taken, the Battlemaster is one of the most durable characters in the game. With the help of shield boosting mods and gear bonuses, he is almost certainly the most durable, with the Krogan Shaman a close second.
Krogan Battlemasters aren't as capable as other krogan at dealing melee damage in a melee damage build, but it is still lethal nonetheless. Since Barrier doesn't give extra melee bonuses, you may as well keep it on, to make sure you're constantly protected. Combine this with the ability to charge, and a krogan Battlemaster is nearly invincible, with only the toughest enemies of the factions (Atlases/Phantoms, Primes/Hunters, Banshees/Brutes/Ravagers or Praetorians/Scions) capable of killing you off quick enough.
A popular option is to bypass melee usage altogether, and use the rank 5 Biotic Charge ability Weapon Synergy instead in conjunction with a strong close range weapon, especially more rapid firing options such as the Reegar Carbine or the N7 Piranha.
Krogan Vanguards are the only class without a grenade or unique power filling up their second power slot. With Carnage being their second power, and it generally being weaker than other powers, its highly recommended to make one's build geared around survivability and skipping said power in order to maximize the potential of the Battlemaster. Opt for protection from Barrier, and use the rank 5 "Martial Artist" evolution in the Fitness skill tree to allow for greater melee damage. Alongside that, make sure the Battlemaster has extra damage protection from when he gets enraged so that the Battlemaster can withstand almost anything.
Phantoms are deadly against krogan since they are much quicker and krogan cannot roll. The krogan does have one major advantage however in that his Biotic Charge will almost always stun a Phantom, even when their barriers are up giving the player a large chance to deal heavy damage. Keep a healthy distance between you and Phantoms to prevent a fatal stabbing, and utilize melee or gunfire and Biotic Charge whenever you can. Keep in mind that Phantoms can perform their one hit kill during your own melee animation, making this always a risky option, so if one must melee it's best to do after a Biotic Charge, although simple gun use may be safer.
Other than that, Guardians are the Battlemaster's only other threat, which can be countered by using a weapon with piercing or a piercing mod. At higher levels of force, Biotic Charge can stun Guardians too, making them lower their shields for a moment and giving the player an opening.
Watch out for Nemeses while closing the distance with them, as one shot will rip the barriers entirely on higher difficulties, while a second shot will deplete health.
Using the Reegar Carbine is rather useful as most enemies have just health or shields/barriers, which makes Phantoms much less dangerous. Piercing mod can solve problems with Dragoons, Atlases and Guardians, as it can easily hit through their shields.
Care should be taken against Banshees, since they cannot be easily staggered, and Brutes, since you cannot roll to evade their charge. Banshees especially can be seen as the Battlemasters' most major threat, although both enemies can also instantly kill you. The Brutes' instant kill radius is much lower than that of a Banshee however, making it relatively easy to stay out of range and making the Banshee a far higher threat.
A trade-off of this to keep in mind however, is while staying close to a Banshee is generally suicide, the Banshee will not perform its grab move when its aura-like, glowing biotic barrier around the Banshee (which also allows it to teleport) is down. This is their moment of vulnerability. Their barrier goes down when they fire a warp projectile or perform their close range burst attack.
Aside from the above point, melee and charge should be used generously.
This is where the Krogan Vanguard will really shine, especially if Barrier is maxed out for damage reduction, and Rage fully evolved for durability. Since no opponent can instantly kill you, you will be able to engage all Geth units at close range, charging to replenish your barriers as needed. With their massive amounts of shields, plus the 25%-40% damage reduction from Barrier, Krogan Vanguards can shrug off practically all attacks on Silver, with only Geth Pyros and Primes posing a significant threat on Gold.
It is much more difficult to melee Geth since some enemies can stun anybody struck by their shots. Time attacks carefully, and stick by your team to avoid any grief. Or otherwise, stick to weapon synergy and firing.
However, the Krogan Battlemaster is immune to most staggering attacks, specially during his melee animations. This makes them one of the most capable units for engaging the Geth directly (the only other characters that are immune to being staggered are the N7 Destroyer and the Krogan Shaman).
Barrier is a must here, as most enemies will be able to strip shields, and then health in just one or two shots each otherwise.
Despite all this, the Geth have no units that can instantly kill, so you can wade into the middle of a group of enemies and smash them with melee attacks and biotic charge without fear of being impaled.
Your ability to tank will prove very useful against the Collectors since they favor ranged combat over melee, but are just as deadly at close range. Praetorians are your biggest problem due to their heavy armor and barriers and deadly twin beam cannons and claws, but you cannot be stunned by any enemies shots.
While not as restricted by Swarms, it still inflicts noticeable grief upon you since as with most vanguards you need to charge to restore shields.
Extreme caution should be exercised when engaging Praetorians, since the Krogan cannot dodge, and because the Praetorian moves quite quickly. Engaging them at melee range is highly inadvisable, since they possess an insta-kill attack, and make use of it frequently.