What causes experience discrepency between members of the same party in Dungeon Defenders?

Question

I have started a new apprentice in the Ranked mode of Dungeon Defenders, along with my brother who has made a squire. Both heroes have started at 0 XP, and have only been played at the same time. Yet up until level 20, I was 5k XP behind, and since then, my character has been steadily going ahead, to the point that I am now 20K XP ahead.

Since we've only compared experience every few level ups, we can't tell which match these differences occurred in.

According to this question and the wiki, experience should be shared evenly among all party members, so I don't know what has caused this.

Answer 1

Only kill XP is shared between players. Other XP gain, such as the various Awards (as listed in Blem's answer) that you can earn at the end of a map, are individually earned and thus can cause this discrepancy. Some of them are flat bonuses, like Knight and Lord, but others, like Invincible (for not taking any damage after the first wave) and Gunslinger (only using weapons and abilities after the first wave) are multipliers (1.3x for those 2 in particular, last time I knew). The values of the flat bonuses vary based on difficulty and map.

For instance, as I was leveling my DPS Huntress, I was able to keep up in experience levels (and sometimes, even outlevel) my other 3 companions because I consistently received the Gunslinger award, giving me 1.3x to my score.

If your Apprentice is using only towers, whereas he is using a mix of towers and character DPS, you may be getting the Master Strategist (used only defenses to harm all enemies after the first wave), consistently, which while it is a flat bonus, really adds up over time. In addition, if you're hanging back and not taking any damage during a wave, whereas he is in melee and getting hit, you may also be getting the No Player Damage (not taking any additional damage during the wave), which is another 1.3x multiplier.

Answer 2

The differences most likely comes from end of wave and mission bonus.

End of Wave Awards

Single-player or Multiplayer

• Knight – Killed 10 enemies in 5 seconds
• Lord – Killed 50 enemies in 5 seconds
• Invincible – Did not take damage for an entire wave after the first
• Master Builder – Kept full Defense Units throughout the wave
• Skin of Your Teeth – Survived a wave after the first with 100 or less Eternia Crystal - Health Points on at least Medium Difficulty

Multiplayer Only

• First Kill – Scored the first kill in the wave
• Janitor – Scored the last kill in the wave
• Chillax – Moved the least distance in the wave

Total Wave Multipliers

• No Core Damage – The Eternia Crystal did not take any additional damage during the wave (1.3x bonus)
• No Player Damage – The player did not take any additional damage during the wave (1.3x bonus)
• Only Used Weapons – Only weapons, familiars, abilities, and environmental hazards were used to damage enemies; non-damaging towers do not count against this award (1.3x bonus)

End of Mission Awards

Single-player or Multiplayer

• Immortal – Did not die throughout the entire match
• Master Strategist – Only used Defenses to harm all enemies after the initial wave. Pet damage stops the player from achieving this award. Not available on Easy difficulty.
• Gunslinger – Only used Abilities & Weapons to harm enemies each wave after the initial wave; non-damaging towers do not count against this award.
• Flawless Victory – No damage to the Eternia Crystal after the first wave
• Boss Slayer – Your Hero or Defense landed the killing blow on a boss

Multiplayer Only

• Banker – Collected the most mana
• Trigger Happy – Initiated combat phase first by activating the core the most times
• Handy Man – Performed the most tower repairs
• Mechanic – Performed the most tower upgrades
• Strategist – Scored the most tower kills
• Most Valuable Hero – Scored the most player kills
• Most Valuable Player – Scored the most combined (player + towers) kills
• Teamwork – Completed a mission with 4 active players

source

Answer 3

Only experience gained from kills is shared between all players, while the killing player will receive the score. The experience you receive as part of your score multiplier is individual, and so if you are outkilling him with your towers (meaning you have a higher base score), even if you both receive the same bonuses (listed by Blem) on the map, you will receive more experience overall.