Tryndamere is not a safe pick btw. Tryndamere gets countered very easily. Teemo is one of them. What tyndamere excels at is the splitpushing. However, such thing can't happen if the enemy team has malphite or renekton top for example, who'll just build armor and clear waves pretty fast and probably beat you 1v1 if they build right. I use tryndamere as a situational pick when the top has pretty squishy champs such as riven, another snowball champion. Good trynd player vs good riven player, good trynd player always wins and denies her farms and kills. Trynd is very effective against riven even in team fights with huge attack dmg reduction with his w(80 at max rank). it's just that not many pros play tryndamere.
There won't be a meta where a riven rushes armor in early game. Riven scales with AD so well that if she rushes armor, she won't get any kills, therefore have no impact in the game. I'd rather go riven mid than face tryndamere top.
When I usually first pick, I go with safe picks who would still do very well without lane dominance. I'm specifically talking about top.