I still recommend mostly armor seals on junglers. It helps keep you healthier due to jungle monsters doing sustained damage and not burst damage where the HP seals usually would help in lane vs possible mixed damage. You get sustain from your jungle item which has better synergy better with armor.
Armor is still really good. It usually comes down to top or bot lane, your champion, your opponent, how aggressive or defensive you think you will play, if you use any amount of armor quints, and if the enemy laner uses ignite or not. I don't think scaling armor seals are as good as scaling hp seals due to the synergy hp has with scaling mr glyphs, how brutalizer and last whisper can nullify scaling armor seals early or later on, a number of decent defensive items (hourglass, frozen heart, abyssal scepter, Athene's, thornmail) do not give health, and because scaling hp and scaling armor makes your laning no different either way.
Mid laners usually go scaling health, flat HP if your early game is weaker or if you are a melee. Vs Zed seals of 5 flat health seals and 4 armor seals for him is really good due to his sustained poke and ignite. 9 HP or Armor Seals vs Zed would also be a solid choice. More armor could be redundant due to the seeker's rush. More HP is bad against Ruined King.