To evaluate Iron Man, I usually compare him with Ronin, because they're both allies you want to slap upgrades on, and with Beast because of the similar stat line. Therefore, if you attach Inspired to each, you get:
Iron Man
6 ER (equivalent resources),
THW 3,
ATK 3,
HP 3
Ronin
6 ER (equivalent resources),
THW 3,
ATK 4,
HP 3
Beast
5 ER (base cost of 5, plus 2 for Inspired, minus a 2-point resource card you get in your hand),
THW 3,
ATK 3,
HP 3
So, with only 1 upgrade card, Iron Man falls behind both Ronin (who has 1 more ATK) and Beast (who costs 1 less ER). If you also attach Reinforced Suit to each, you get:
Iron Man
7 ER,
THW 3,
ATK 3,
HP 5
Ronin
8 ER,
THW 3,
ATK 4,
HP 5
Beast
7 ER,
THW 3,
ATK 3,
HP 5
In this case, Iron Man becomes equivalent to Beast, while compared to Ronin, you're trading 1 more ER for 1 more ATK (personally, I'd still choose both Beast and Ronin over him).
Conclusion: Iron Man becomes truly competitive only in a full Voltron scenario with 3+ upgrades, which however is far from easy to achieve. While not terribly subpar, he's now an outdated card and definitely could've been given more love (1 more HP would probably do the job, maybe also adding a thematic Aerial trait).