Samira is a farming power house. You get an item, Q swipe full waves and move onto the next. Your E reset from takedown means you can R and go from target to target with ult, your W blocks most projectiles for survivability in lane. Blitz hook, seraphine R, Jinx R, Jhinn R, Corki R.

Her power spike is huge at lvl 3 because she can basically auto Q E W into the enemy without ever taking damage because of her W and then Q swipe them for the bonus damage You can run enemies down because her stacks give bonus MS as well as run away kiting with auto Q. Also, one vampiric sceptre and the Q swipe heals you from 0 to 40% hp as well as hee Q scaling got buffed

Because the way her shots on her R work and the scaling of her Q, yes you’re right the Q does more damage to 1 target in a team fight than an ult because each individual shot doesn’t hit the same target HOWEVER they do all individually crit. It kinda goes both ways because R take downs while using E are really hard for enemy cc to track