Lethality is designed to kill squishes, it's best use is against champs that don't build Armor or build very little. This includes Ap/Ad Carries, Assassins(most of them atleast), BURST MAGES and Enchanter's.
The issue with the items you listed is for 1, seraphs, rylai's, rod and Liandries aren't good on Burst Mages. Rod takes to long to get to it's spike, burst mages scale best into mid game, seraphs takes to long to stack when burst mages have high cooldowns and high mana costs, liandries is built to work against tanks but a burst mage isn't gonna be doing anything to a tank anyway and Rylai's was nerfed and since then is pretty useless on pretty much every mage except Swain.
Swain, Vlad, Galio and Rumble are "Battle Mages" they have short cooldowns, low mana costs and deal less damage.
Syndra, Lux, Ahri and Zoe are "Burst Mages" they have longer cooldown's, higher mana costs and deal a lot of damage, they don't scale well with resistances or health.
Ryze, Cassiopeia, Azir and Xerath are "Artillery Mage's" they have mid range cooldowns, high early mana costs but get a lot of mana later on and deal consistent DPS making them "AP Carries." they scale better with Health and Resistances than burst mages but not as well as Battle Mages.
Each one builds different based on the type, the issue though is mainly for Battle Mages and AP Carries, you can build as much HP as you want but with no resistances an ADC can burst you in an auto attack as either of them. The only saving grace for Burst Mages is that you can kill them before they kill you. Not to mention as all of them against an AD matchup you lose the early game because of Hexdrinker, free AP damage shield with MR tacked on? Sign me the fuck up if i'm playing a Talon VS ryze match up, watch me mop the floor with his shiny ass forehead dude, it's easy.