It's Got Some Heft is a talent that gives Caspian some really bonkers burst with War, and with the recent base attack speed buff, the downside is a little less noticeable. It's probably his best talent right now, but it can be tricky to get value out of.
The gameplay loop revolves around popping Tempo to get your stacks quickly and using those stacks to burst people down with War. One full combo of War with this talent is enough to kill a squishy. For this reason, duration on Piercing Momentum is more important than Sharp to increase the effectiveness of the talent, and I actually don't recommend using duration on Sharp stacks at all.
The only necessary cards are Casual Competency 5, In The Thick of It, and He Shot First. Other than that, you can fill the deck however you want. I like to use Swift Strikes and Deadly Flourish because base Deadly Momentum kinda sucks.
Casual Competency is for the stacks, definitely need this one at level 4 or 5. In The Thick of It gives you enough ammo for one War combo per level, so you can run it at whatever level you want but I think level 2 is more than enough. He Shot First for more uptime on Casual Competency, you can never have too much of this card in my opinion, but I usually stick with level 3. I don't recommend using The Finer Things with this talent because you'll want to be mostly using War anyway, and you'll want to buy Nimble first anyway so it's kinda obsolete
Nimble is by far the most important item, and should usually be rushed to level 3. After this, it really depends on the match. Resilience and Kill to Heal are always good, but I also think Chronos is a decent choice if you have the extra credits. It lets you throw stuns out way more often, and therefore get stacks more often. That being said, most other items are still going to be better.
Hitting an enemy with Rogue's Tempo grants you 5 stacks of Piercing Momentum and Sharp Momentum.
He Shot First
Extend the duration of Piercing Momentum stacks gained by hitting with Love by 36%.
Increase the travel speed of Deadly Momentum by 24%.
In The Thick of It
Generate 6 Ammo after hitting at least one enemy with Rogue's Tempo.
Increase the travel distance of Deadly Momentum by 10%.
It's Got Some Heft
Increase the Range and Damage of War, but decrease its rate of fire. War's attacks now deal an additional 20% damage to each enemy hit for each enemy hit in total with your attack.
Gain 21% Movement Speed.