For Aegislash, your team seems to be fairly special focused with Gardevoir and Charizard, so physical set would probably be best right off hand. Invest in Special defense evs primarily.
King's Shield is a must of course, letting you play gotcha with the AI, and giving your Pokemon significant staying power.
For physical attacks Shadow Claw and Iron Head give STAB, and will hit for at least neutral on most Pokemon. For the final move you can go with Sacred Sword for additional coverage against Dark Types, Swords Dance to allow for a physical attack boost that will allow Shadow Claw and Iron Head to rip through everything more than Aegislash already does, or my personal pick: Toxic. Toxic gives King's Shield additional utility, and the residual damage rapidly weakens opposing Pokemon.
For Swampert I see two directions. First make it the Aegislash mirror, focusing on Physical bulk rather than special bulk. Then load it up with Stealth Rocks, Roar, Earthquake, and Scald. That will give it the ability to get build up entry damage off of Stealth Rocks and Roar, while giving your team attacking ground and water attacks. The alternative is an all-out attacking set with a Choice Band. It naturally learns Earthquake and Rock Slide, can can be taught Waterfall and Ice Punch, giving wide coverage and relying on its natural bulk and lack of weaknesses apart from grass to keep it alive to attack.