The basic WoD mechanic is quite serviceable. Attribute + Skill (+mods) + d10, compare to success chart for degree of success. However beyond this basis there's actually quite a bit of complexity. You have your Attribute and Skill but now comes the question, is it an Instant test? Extended? Extended slow and steady? The unofficial Instant/Extended hybrid that is combat attacks? And why dose Initiative work completely differently than any other test in the system?
Now obviously at some point you start devolving into subsystems but the fast divergence into different test types mean that I've lost count of the number of times I've had to explain that no, 5 successes on an extended test is not an exceptional success, no, you don't redraw 10's for Initiative, no, you can't just pile more successes on that failed extended challenge. If everything used the same test structure then at least I'd save all the bloody time and trouble taken to explain the above and more time and time again.
Now it's easy to see why there are so many test types. Officially Instant tests only normally give one of four result: Dramatic Failure, Failure, Success, or Exceptional Success. Even when you count successes Instant tests are kinda terrible at representing long term action, as demonstrated by the Instant test vs long travel time of hedge journeys. Even odds by the end of it no-body remembers or cares who's driving...
So, boldly on to the point. Wouldn't it be convenient if all (or at least more) tests worked in the same way? Subsystems based on the same test output? Certainly from experience I find it easier to explain to new players how hedge travel and perception work but the instant Initiative gets rolled everything gets all confused. Because Instant tests alone are lacking for some challenges and even most Instant tests could do with a bit of the Extended's "it's how long you take" philosophy I propose changing over to a system in which the basic test is a Instant/Extended hybrid like combat: Every test has clear results but those results can build over time to a final goal. The test would work as follows:
Step 1: Forming the Test Pool
Attribute + Skill. Modifiers are also applied, with several categories of bonus and penalty being especially common.
• Equipment bonus. It's easier to hurt someone with a pointy stick than with your bare hands.
• Difficulty. When acting against another character this is often an Attribute, usually a Finesse one. It's hard to hit someone who's Dexterous, troublesome to pin down a Manipulative bastard in a lie, and a pain in the ass to follow the tracks of someone with enough Wits to muck up their trail. When there isn't an opposing side to a test then difficulty will likely be set by some other trait or arbitrarily based on the complexity of the action.
• Environmental. Sometimes a bonus, sometimes a penalty but the conditions can make a significant difference in one's expected rate of success.
Step 2: Getting Successes
Draw some cards, throw some fingers, or otherwise simulate a d10. Add this to your Test Pool and determine your successes (9 is 1 success, 12 is 2 successes and so on). If you Fail or Dramatically Fail then the ST takes over and bad things might happen.
Step 3: Determine Severity (Optional)
In a simple test we might only care about success/failure. In that case skip this step.
In many cases characters are attempting to make some change to the world. In this case we want to know the Severity of that change. This Severity is calculated as the testers Advantage - the tests Resistance. The Advantage is one of the character's Attributes, often a Power Attribute. The tests Resistance is an Attribute of the defender, often a Resistance Attribute, when there is a defender. When there is no defender the test Resistance is often defined by another trait (Durability) or based on the situation. Some things may modify Severity, such as tools or armor.
Step 4: Spending Successes (Optional)
If the player is satisfied with basic success at their current Severity they can skip this step.
Successes can be spent on "upgrades." One of the most common upgrades is to increase or decrease the Severity by one per Success spent. Different tests have different upgrades. A stab wound might be bleeding out while an impassioned argument might not only convince a character to join a cause but to bring in others as well. When traveling the hedge each Success on navigation can be spent to remove one character from consideration when determining travel time.
Successes can even be spent on additional similar actions using the same test pool. For example one might throw the sword from an opponents hand as well as cut them. These extra actions treat the character's Advantage as 0 for calculating base Severity.
Step 5: Resolution
Apply all effects of the test.
Sidebar: What about my other hand?
Usually characters will be doing one thing at a time. Sometimes however multiple things need doing at once, such as trying to shoot out an opponents tires while driving in the car chase. Characters suffer a -5 to the test pools of all actions for each action after the first.
Sidebar: Everyone wants to do something
When several characters all want to do things time is broken into rounds, each about a minute long. First everybody declares their character's action for the round. Then everybody dose the tests for their character's actions and results are applied simultaneously. The results of the tests represent the aggregate result of the characters attempt(s) over the round. A character might attack with a weapon many times but only connect a few times, for example. Characters can make a Dexterity + Composure? Initiative test to have one of their actions be applied before others in the round but doing so will, obviously, mean doing two things in the round and taking the appropriate penalty.
Sidebar: Didin't you just make the game so much more complicated?!?
Not really. Simple tests can still throw out the optional steps and be handled with a quick "Attribute + Skill + d10, is it 9+?". However the added complexity of this mechanic over what's in the core book's basic test mechanics (my half page to their short, quick 10+ pages) can be more than made up for when combat is reduced from 50 pages to about three pages covering how Severity converts to physical trauma and some example test pools. I will post up some examples of how this all could work in play later but (imo) the above should be clear enough that one can see how you might get injuries, sway, or crafting out of it.