Bomb items are more considered as an secondary damage sources even when you have a farming skills; Offense and Summon spells. (From my point of view).
To be a little more specific, advance players used them under these condition.
-Provide a secondary damage source with summon skills
-Provide a strong farming potential before 1st duel.
-Counter hyper-gank build by killing your spawn faster
Although getting tiara (Decent mana item) as starter is also a good choice for optional item that can be build into late game (Immortal items)
Personally, a power late game build like Pure Crit/ Pure armor reduction/ 4x stuns skills can be very difficult to translate it into late game, because most experiences players can divided their funds through early-mid-late game without having to sell a sin
gle items or transform it into something else... (Resell).
To be short, even if you can reach late game with pure build. It is still impossible to win against players with high stats (20k+ above) + 4x immortal rings/armor/boot. BLAST! (Just a theory, but I'd imagine it'll take like 3 hours at least to hit that kind of stats.. O.o)
