to give examples
On blood boil you've got Ars Baalos with 1 facet, +6 blood boil, +5 demonic mastery, +2 bind demon, +2 defiler. Then as freebies its got 15% ctc decrep and high defense (mostly irrelevant), +1.5 life/clvl (nice extra life overall) and +10% dr (big bonus)
So the best possible magic could be something like +3 demon skills / +3 blood boil / +3 bind demon / +3 defiler with 2 sockets. An unimaginably astronomcially unlikely item, and then all you've got over ars baalos for damage is 1 extra facet. But you lose that huge life/dr and other bonuses.
on fire warlock you could have what, +6 flame wave / +6 apocalypse? But you're trading 30% / -5% for 10% / -10%, and still lose +1 to apocalypse and FCR and huge MAEK and some resists and so on. Ars diabolos is just better overall
on echoing strikes you need to give up 115% ed and 30% fcr to get +4 skills? Maybe just maybe an obsession build could do it and have 2x ed jewels to make up the difference
overall it takes insanely hard to obtain magic tomes to achieve what the uniques do when they drop 1000000x more often