You should not worry if you think your not going anywhere with lead playing. You have to constantly knock on that block till you get it.
Yes you should concentrate on timing and rhythm as you never see Jimmy Paige playing a solo thoughout a Led Zep concert or Hendrix just widdling for 12 hours. Even Petrucci keeps rhythm half the time, unique rhythm and time signatures too.
Get a drum beat/machine going or a metronome, start tapping your foot, and start playing chords to the beat, changing every other bar. Maybe you could play a barre A chord in 4/4, 4 to the bar for two bars. Change to a barre D or barre G for the next 2 bars. Then try that in open E and open D and Am. Mute the strings after ever beat. Keep it constant and steady!
Better yet, play along AC/DC =] then go up to Metallica ==}
As you get better with time, go learn what is a scale and chromatics, practice chromatics, then scales, then start jamming~