Lottery abilities

This is a follow on form my post on removing random from combat. In that I said I wanted to remove most random chance from my games basic combat. I also said I wanted to keep some positive random events that help the player and give them a 'wow' factor. I call these lottery abilities, and by this I mean abilities that have a low random chance to fire, but that are very powerful when they do. The most common ones I've seen are dodge, critical hit and counterattack.

Critical strike

A crit is where an attack causes extra damage, usually double. The first I became aware of it was way back playing D&D and rolling a natural 20, but it's in a huge number of games and it's very popular. There's just something hugely satisfying about getting the aforementioned CRITICAL STRIKE and decimating your opponent. It's also easy to produce cool visual and  audio effects to go with it. In some game is only applies to melee attacks, not to ranged or magic, to give melee attacks a boost. There can also be spells or abilites that give you an increased or guaranteed critical chance.

Dodge

Dodge is simply where a character completely evade another character’s attack. It’s present in a huge number of rpgs and roguelikes. Usually whether the attack is dodged or not it worked out by rolling the old random number dice depending on the attacker’s skills and the defenders skill levels. Sometimes it will be taken off of things like dexterity or agility, sometimes there’s a direct ‘dodge’ or ‘dodge reduction’ stat.

The fact that dodging completely negates an attack makes it hugely powerful. Care needs to be taken because if a character has too much dodge it can be completely game breaking.

It also has an additional problem in that it's difficult to make it exciting, in effect it's an action not taking place. You can't really have the cool blood splatter CRITICAL STRIKE excitement when all you're effectively saying is 'nothing happened'. A critical strike can end the fight but all a dodge does is prolong it, abait in your favour.

Counterattack

A chance that an attack will immediately trigger an attack out of turn in revenge from the character who was attacked. This can be cool when it works but can also be confusing. Again it can be hugely powerful and almost game breaking in excess.

The problem with these abilities

These abilities can completely change an encounter when they go off. This can feel great when it happens in your favour, but on the other hand it feels horrible and unfair when it you're on the receiving end, so care needs to be taken. They can easily break pvp games, but luckily in a pve game the npcs don't mind you dodging all their attacks then critting them for half their health with a counterattack.

There's also the argument that too much random ruins fights and takes the skill out of them. Players can play a slow game just hoping for a lucky crit instead of playing tactically, then get frustrated when the crit doesn't happen or goes against them.

What to do about them

• Soften the effects by having gradations. It's quite common for games with critical strike to have ways to either increase the damage a critical strike does or to reduce the additional damage an enemy crit does. This leads to more predictable damage incoming with less likelihood of the player losing because of an unlucky spike. This is especially important in a game with permadeath. Dodge can also have an idea of only dodging portions of the attack – glancing blows.
• You could also add extra stats that directly counter these abilities, reducing an enemy’s chance to dodge your attack or crit or counter you. 
• Remove the lottery element and just have them as status effects that give an effect for a duration – for example a skill that means you a have a very high chance to dodge the next X attack.
• Make it so the enemies can't do them to you, or at the least do some very infrequently.
• Make sure the chances to trigger the attacks stay very low. Once you get a high enough chance that you can reliably expect one of these effects to go off in a fight they stop being lottery effect. If the player is think 'shit I was so unlucky not to get a crit in that fight' I know the chances are too high.